نماذج الوزارة باللغة الانجليزية فى الفيزياء وورد كمان للتعديل2021

FIRST: EXAMS ON Chapter (1)

Electric current, Ohm’s law and Kirchhoff’s Laws

Complete:

When a current of intensity 3A passes through a point in an electric circuit, the electric charge passing through one minute equals …….

The voltage difference required to let a current 3A pass through 6 Ω resistor equals …….

If the voltage difference across a 2 Ω resistor is 6 V , the current intensity is ……..

If two equal resistances 1 Ω each are connected in series, the equivalent resistance is ……….., but if they are connected in parallel, the equivalent resistance is …….

The emf is measured in the same unit as …………..

In the circuit shown:

The ammeter reading is ..........

The voltmeter reading is ..........

In the circuit shown:

The ammeter reading A1is ..........

Choose the right answer:

Four lamps 5 Ω each are connected in parallel. The combination is connected to a 12 V battery with negligible internal resistance:

The current in the battery equals …………….

a) 8 A b) 6 A c) 4 A d) 2 A e) 72 A

The total chargea leaving the battery in 10 s is …………….

a) 80 C b) 60 C c) 40 C d) 20 C e) 2 C

The current in each lamp …………….

a) 3/2 A b) 8 A c) )2/3 A d) 1 A e) 2 A

The voltage difference across each lamp is …………….

a) 3 V b) 12 V c) 6 V d) 2 V e) 4 V

The total resistance of the four lamps is …………….

a) 2/3 Ω b) 24 Ω c) 3/2 Ω d) 6 Ω e) 12 Ω

If the four lamps are connected in series, the total resistance is …………….

a) 2/3 Ω b) 24 Ω c) 3/2 Ω d) 6 Ω e) 12 Ω

Essay Questions:

Show how to prove that the equivalent resistance of 3 resistors connected in series is given by : R=R_1+R_2+R_3

Show that the reciprocal of the equivalent resistance of 3 resistors connected in parallel is equal to the sum of their reciprocals.

What are the factors determining the resistance of a conductor ?

Problems:

Calculate the total resistance in the circuit shown and also the total current if the internal resistance of each cell is 2 Ω.

(20 Ω & 0.75 A)

Determine the equivalent resistance of a bunch of the resistors shown.

(2.5 Ω)

The circuit shown in the figure consists of a 15 V battery , an external resistance 2.7 Ω and a switch. If the internal resistance of the battery is 0.3 Ω, determine:

The reading of the voltmeter V when the switch is open, assuming that the voltmeter resistance is infinite. (15 V)

The reading of the voltmeter when the switch is closed. (13.5 V)

A student wound a wire of a definite length as a resistor. Then he made another of the same material but half the diameter of the first wire and double the length. Find the ratio between the two resistors. (1:8)

A copper wire 30 m long and 2×〖10〗^(-6) m^2 cross sectional area has a voltage difference of 3 V across its terminals. Calculate the current intensity if the copper resistivity is 1.79×〖10〗^(-8) Ω.m. (11.17 A)

A 5.7 Ω resistor is connected across the terminals of a battery of 12 V emf and 0.3 Ω internal resistance. Calculate:

The current intensity passing in the circuit. (2 A)

The voltage difference across the resistor. (11.4 V)

Analyze the given circuit in the opposite diagram using Kirchhoff’s law to find:

VB1 and VB2 .

The voltage drop across eb.

(15 V , 5 V , 8 V)

Find the equivalent resistance of the given resistance network using Kirchhoff’s law.

(1.18 Ω)

A wire of length 30 m and cross-section area 0.3 〖cm〗^2 connected to a DC source and ammeter of negligible resistance in the closed circuit, if the electric current passing through the wire is 2 A and the potential difference at its ends 0.8 V. Calculate the conductivity of the wire. (25 x 〖10〗^5 Ω^(-1).m^(-1))

A wire of length 2m and cross section area 0.1 cm2 is connected to a source of 10 V emf, then a current of intensity 2 A passed through it.

Calculate the resistivity and the electric conductivity of its material.

(25×〖10〗^(-6) Ω.m & 4 x 〖10〗^4 Ω^(-1).m^(-1))

A wire of a uniform cross-section carries a current of 0.1 A, when the potential difference between its terminals is 1.2 V. If a square abcd is made of this wire, calculate the equivalent resistance for the wire when :

The power source is connected to points a, c.

The power source is connected to points a, d. (3 Ω & 2.25 Ω)

Three resistors 10 Ω, 20 Ω, 30 Ω are connected together to electric source where the electric current intensity passing in each resistor were 0.15 A , 0.2 A , 0.05 A respectively. Shows by drawing how are they connected. Then calculate the total resistance of the circuit. (27.5 Ω)

Two resistors 300 Ω, 400 Ω are connected in series to 130 V power supply.

Calculate the readings of a voltmeter of resistance 200 Ω when connected across:

The two terminals of the first resistance.

The two terminals of the second resistance. (30 V & 40 V)

A battery of emf 12 V and its internal resistance is 0.5 Ω. Calculate the percentage of the voltage drop in the battery when it is used to light a lamp of resistance 2 Ω. (20%)

A power station is connected to a factory 2.5 km away by two wires. The potential difference between the terminals of the wires at the station 240 V and that for the other terminals at the factory is 220 V, if the factory is using a current of 80 A. Calculate:

The resistance of each meter of the wire.

The radius of the wire if the resistivity of its material is 1.57×〖10〗^(-8) Ω.m.

(Knowing that π=3.14)

(5×〖10〗^(-5) Ω & 0.01 m)

First Exam

Question One:

Write down the scientific term:

The physical quantity equals the resistance of conductor its length 1 m and its cross-sectional area 〖1 m〗^2 at certain temperature.

………………………………………………………………………………………………………………………………………………………………………….

The potential difference between the terminals of conductor its resistance 1 Ω and pass current 1 A through it.

………………………………………………………………………………………………………………………………………………………………………….

The resistance of conductor that allow to pass the electric current intensity 1 A when the potential difference between its terminals equal 1 V.

………………………………………………………………………………………………………………………………………………………………………….

The law which states that the current intensity passing through a conductor is directly proportional to the potential difference between its terminals.

………………………………………………………………………………………………………………………………………………………………………….

The quantity of charge resulting from passing current intensity 1 A through a cross-sectional area in 1 sec.

………………………………………………………………………………………………………………………………………………………………………….

First: Mention TWO factors affecting on:

The electrical conductivity of conductor.

………………………………………………………………………………………………………………………………………………………………………….

The resistance of the wire.

………………………………………………………………………………………………………………………………………………………………………….

The electrical current intensity passing through the battery when the circuit is closed.

………………………………………………………………………………………………………………………………………………………………………….

Second: Compare between each of:

The electrical resistance and the electrical resistivity (with respect to the unit of measurement).

………………………………………………………………………………………………………………………………………………………………………….

The current intensity and the potential difference (with respect to the used measurement device).

………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….

Kirchhoff’s first law and Kirchhoff’s second law (with respect to the scientific concept which depend on).

………………………………………………………………………………………………………………………………………………………………………….

A voltmeter of resistance 500 Ω was connected in parallel with unknown resistance and then an ammeter was connected in series with them. When the terminal of this group was connected with battery, the reading of ammeter was 0.01 A and the reading of voltmeter was 3 V. Find the value of the unknown resistance.

Question Two:

Give the scientific reason for:

Decreasing total resistance for a group of resistances by connecting them in parallel.

Increasing the total resistance for a group of resistance by connecting them in series.

Changing the potential difference between the terminals of the electric source by changing the total resistance in the circuit.

Changing the resistance of the rheostat (variable resistance).

Connecting home devices and lamps in parallel.

First: Write down the mathematical formula:

Kirchhoff’s first law.

………………………………………………………………………………………………………………………………………………………………………….

The resistance of a conductor in terms of its resistivity.

………………………………………………………………………………………………………………………………………………………………………….

Ohm’s law for closed circuit.

………………………………………………………………………………………………………………………………………………………………………….

Second: Mention the equivalent unit for:

The ohmic resistance.

………………………………………………………………………………………………………………………………………………………………………….

The electric current intensity.

………………………………………………………………………………………………………………………………………………………………………….

The electric power.

………………………………………………………………………………………………………………………………………………………………………….

From the shown figure for the electric circuit, calculate:

The potential difference between the points (a&b) (V_ab).

The electromotive force (V_B).

The value of the resistor (R).

………………………………………………………………………………………………………………………………………………………………………….

Question Three:

Choose the correct answer:

If the resistance of the voltmeter in the opposite figure is 100K Ω, with neglecting the internal resistance of the battery, so its reading equals ……

Zero

2 V

3 V

4 V

When we connect some equal resistances in series, the equivalent resistances is 100Ω and when we connect them in parallel the equivalent resistance is 4 Ω, so the value of each of them is………..

10 Ω

20 Ω

30 Ω

40 Ω

The reading of the voltmeter in the opposite circuit equals………

4 V

6 V

8 V

12 V

Three identical lamps was connected in series with the source has a negligible internal resistance then they was connected in parallel with the same source, so the ratio between the consumed power in the two cases respectively is…………

1 : 2

1 : 3

1 : 6

1 : 9

What will happen to brightness of the lamps (A) & (B) in the circuit when the slider of rheostat moves from (X) to (Y)?

(neglecting internal resistance)

Lamp (A) Lamp (B)

(A) Doesn’t change Increases

(B) Increases Increases

(D) Increases Decreases

First: The below graph shows the relation between the potential difference through two wires (A) & (B) and the current intensity passing through them, if the two wires have the same length and area.

Which wire has the greater resistance? And why?

If the two wires are connected in parallel with the source, which of them will consume more power? Why?

………………………………………………………………………………………………………………………………………………………………………….

Second: If you have a copper wire of known number of turns (N) and radius (r) wounded around a pulley in a form of circular coil such that the terminals of the wire appear. Explain with experimental steps to determine the resistivity of copper by using only battery, switch, ammeter, voltmeter, some connecting wires and ruler.

………………………………………………………………………………………………………………………………………………………………………….

A bar of mercury in tube has length 106.3cm and cross-sectional area 〖1 mm〗^2 and its resistance 1 Ω.Calculate:

The resistivity of the mercury.

The conductivity of the mercury.

………………………………………………………………………………………………………………………………………………………………………….

Question Four:

Give reason for:

It is necessary to have a potential difference between conductor terminals to transfer the quantities of charges through it.

………………………………………………………………………………………………………………………………………………………………………….

The conductivity of the material doesn’t change by changing its dimensions.

………………………………………………………………………………………………………………………………………………………………………….

The potential difference between the terminals of the source equal the emf of the source in case of no current passes through the circuit.

………………………………………………………………………………………………………………………………………………………………………….

The rheostat can control the current intensity passing in the electric circuit.

………………………………………………………………………………………………………………………………………………………………………….

The resistance of the conductor decreases by increasing its cross-sectional area at constant length and temperature.

………………………………………………………………………………………………………………………………………………………………………….

First: What is meant by?

The work done to transfer quantity of charges 50C between two points equal 500J.

………………………………………………………………………………………………………………………………………………………………………….

The current intensity passing through a conductor equals 5A.

………………………………………………………………………………………………………………………………………………………………………….

The resistivity of the copper at a certain temperature equals 1.68×〖10〗^(-8) Ω.m.

………………………………………………………………………………………………………………………………………………………………………….

Second: Prove that if we connect three resistances in series, the equivalent resistance of them equal R_eq=R_1+R_2+R_3

………………………………………………………………………………………………………………………………………………………………………….

This following table records the change in the potential difference between the poles of a battery with the changing the current intensity passing through it:

V (Volt) 8 7 5 3 1 B

I (A) 0.5 1 2 A 4 4.5

Draw the relation of the given data as the potential difference represented on the vertical axis, and from the graph Find:

The value of both (A) and (B).

Emf of the battery.

Internal resistance of the battery.

Second Exam

Question One:

Write down the scientific term:

The reciprocal of a wire resistance its length 1 m and has cross-sectional area 〖1m〗^2 at certain temperature.

………………………………………………………………………………………………………………………………………………………………………….

The work done to transfer quantity of charge 1C between the terminals of a conductor.

………………………………………………………………………………………………………………………………………………………………………….

Its value equals to the potential difference between the terminals of battery in an open circuit.

………………………………………………………………………………………………………………………………………………………………………….

The law which states that the algebraic sum of the currents flowing into anode equal to the currents flowing out of it in a closed circuit.

………………………………………………………………………………………………………………………………………………………………………….

The quantity of electric charges passing through a conductor.

………………………………………………………………………………………………………………………………………………………………………….

First: Mention One factor affecting on:

The resistivity of the conductor.

………………………………………………………………………………………………………………………………………………………………………….

The electric current intensity passing through a conductor connected in series with source of negligible internal resistance.

………………………………………………………………………………………………………………………………………………………………………….

The direction of quantity of electricity flowing between two points in closed circuit.

………………………………………………………………………………………………………………………………………………………………………….

Second: Compare between each of:

The resistivity and the conductivity of the silver (with respect to the effect of decreasing the temperature of the conductor).

………………………………………………………………………………………………………………………………………………………………………….

The potential difference between the terminals of each of two wires connected in series having same length and cross-sectional area, one of them made from copper and another from platinum (neglecting change in temperature). Knowing that the resistivity of copper is less than the resistivity of platinum.

………………………………………………………………………………………………………………………………………………………………………….

The potential difference between two points and the emf of a source (with respect to the scientific concept).

………………………………………………………………………………………………………………………………………………………………………….

In the circuit shown, by using Kirchhoff's laws.

Find:

The current intensity passing in each branch.

The electric potential at point (A).

………………………………………………………………………………………………………………………………………………………………………….

Question Two:

Define:

Kirchhoff's second law.

………………………………………………………………………………………………………………………………………………………………………….

Ohm.

………………………………………………………………………………………………………………………………………………………………………….

The resistance of a conductor.

………………………………………………………………………………………………………………………………………………………………………….

Ampere.

…………………………………………………………………………………………………………………………………………………………………….

………………………………………………………………………………………………………………………………………………………………………….

The electric current intensity.

………………………………………………………………………………………………………………………………………………………………………….

First: Write down the mathematical formula:

Ohm's law.

………………………………………………………………………………………………………………………………………………………………………….

The electric power.

………………………………………………………………………………………………………………………………………………………………………….

Kirchhoff's first law.

………………………………………………………………………………………………………………………………………………………………………….

Second: Mention the physical quantities and an equivalent measuring unit:

A.Ω

………………………………………………………………………………………………………………………………………………………………………….

A.s

………………………………………………………………………………………………………………………………………………………………………….

Ω^(-1) m^(-1)

………………………………………………………………………………………………………………………………………………………………………….

In the opposite figure: What is the reading of the ammeter and voltmeter in each case (neglecting internal resistance)?

Opening switches (S_1) and (S_2) together.

Closing switches (S_1) and (S_2) together.

Closing switch (S_1) and opening (S_2).

………………………………………………………………………………………………………………………………………………………………………….

Question Three:

Choose correct answer:

If the current intensity passing through the resistance (R_1) is 2 A then the equivalent resistance of the circuit equals............

3 Ω

4 Ω

6 Ω

12 Ω

In the circuit shown, the value of resistance (R) equals.......

2 Ω

4 Ω

6 Ω

8 Ω

In the opposite figure, if the current intensity passing through resistance 2 Ω equals 1 A, so the current passing through resistance 12 Ω equals.........

0.5 A

1 A

1.5 A

2 A

In the opposite figure, if we connect a battery of negligible internal resistance between (X & Y), then the equivalent resistance between (X & Y) equals.....

2 Ω

4 Ω

6 Ω

8 Ω

In the previous figure, if we transfer the battery from its position to the position of the resistance 7 Ω, then the equivalent resistance of the circuit becomes.........

43 Ω

42 Ω

41 Ω

40 Ω

First: When each of the following pairs of the physical quantities are equal numerically?

The resistance of the wire and the resistivity of its material.

………………………………………………………………………………………………………………………………………………………………………….

The current intensity passing through conductor and the potential difference between its terminals.

………………………………………………………………………………………………………………………………………………………………………….

Two current intensities passing through two different resistance connected together in a closed circuit.

………………………………………………………………………………………………………………………………………………………………………….

Second:

In the opposite figure three identical lamps connected with a battery of negligible internal resistance, what will happen to the brightness of lamp (B) when the switch (S) is closed (with explanation)?

In the previous question, if the internal resistance is not neglected, what will happen to the brightness of lamp (B) when the switch (S) is closed (with explanation)?

………………………………………………………………………………………………………………………………………………………………………….

In the circuit shown, by using the Kirchhoff's laws. Find:

The reading of the ammeter.

Potential difference between (A) and (B).

Potential of point (X).

………………………………………………………………………………………………………………………………………………………………………….

………………………………………………………………………………………………………………………………………………………………………….Question Four:

Give reason for:

The resistance of the wire changes when the temperature is changed.

………………………………………………………………………………………………………………………………………………………………………….

The resistivity of the material of conductor doesn't change when the cross-sectional area changes.

………………………………………………………………………………………………………………………………………………………………………….

When three lamps were connected in series with a battery, the brightness of them differ than when connected them in parallel with the same battery.

………………………………………………………………………………………………………………………………………………………………………….

The potential difference between the terminals of the battery is less than its emf.

………………………………………………………………………………………………………………………………………………………………………….

The resistance of the conductor increases with increasing its length at constant area and temperature.

………………………………………………………………………………………………………………………………………………………………………….

First: What are the results that could be happen to each?

The conductor resistance, when increasing the current intensity passing through it to the double at constant temperature.

………………………………………………………………………………………………………………………………………………………………………….

The resistivity of a metal conductor material, when increasing the length of the conductor to the double.

………………………………………………………………………………………………………………………………………………………………………….

The total resistance of an electric circuit, when connecting a group of resistors in series with the electric source.

………………………………………………………………………………………………………………………………………………………………………….

Second: Write down the slope for:

…………………………………………….

………………………………………….

.............................................

The following table records the ohmic resistances for many wires of the same metal, the length of each is 12m with the reciprocal of the area for each of these wires.

R (Ω) 6 7.5 10 15 23 30

1/A×〖10〗^6 m^(-2) 2 2.5 3.3 5 7.7 10

Draw a graph representing this data, when the resistance (R) on Y-axis and reciprocal of the area (1/A) on the X-axis, and from the graph Find:

Resistance of the wire of same material and length while its cross-sectional area is 0.0025 cm^2.

The conductivity of the wire material.

SECOND: EXAMS ON Chapter (2)

MAGNETIC EFFECT OF ELECTRIC CURRENT

Essay question:

State the parameters on which the magnetic flux density depends in each of the following cases:

Around a long current-current straight wire.

………………………………………………………………………………………………………………………………………………………………………….

At the center of a circular loop that carries current.

………………………………………………………………………………………………………………………………………………………………………….

At any point on the axis of a current –carrying solenoid.

………………………………………………………………………………………………………………………………………………………………………….

What are the parameters affecting the magnitude of the force with which a magnetic field acts on a current-carrying wire placed at right angles to the field?

………………………………………………………………………………………………………………………………………………………………………….

Prove that the force F acting on a long wire B of length carrying current I and placed at right angles to a magnetic field of flux density B is determined by the relation: F=BIl

………………………………………………………………………………………………………………………………………………………………………….

Prove that the torque 𝛕 acting on loop of face area A, number of turns N, carrying a current I and placed parallel to a magnetic field of B flux density is τ=BIAN

………………………………………………………………………………………………………………………………………………………………………….

Describe with the aid of a labeled diagram the construction of the sensitive galvanometer and explain its basic operation.

………………………………………………………………………………………………………………………………………………………………………….

Explain how the sensitive galvanometer is converted to be used as an ammeter.

Deduce the required relation.

………………………………………………………………………………………………………………………………………………………………………….

Explain how the sensitive galvanometer is converted to be used as a voltmeter.

Deduce the required relation.

………………………………………………………………………………………………………………………………………………………………………….

Give reasons for:

Mounting a soft iron cylinder inside the coil the galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

The coil of the moving coil galvanometer is attached to a pair of springs.

………………………………………………………………………………………………………………………………………………………………………….

When the moving coil galvanometer is used as a voltmeter, a resistor of high resistance is connected in series with its coil.

………………………………………………………………………………………………………………………………………………………………………….

An ammeter is connected in series with a circuit, but the voltmeter is connected parallel to it.

………………………………………………………………………………………………………………………………………………………………………….

Connecting a constant resistor inside the ohmmeter.

………………………………………………………………………………………………………………………………………………………………………….

The cell connected to the ohmmeter should have a constant emf.

………………………………………………………………………………………………………………………………………………………………………….

What is meant by each of: potential multiplier and shunt? What is the use of each?

Deduce the rule related to each.

………………………………………………………………………………………………………………………………………………………………………….

Explain how you can use the moving coil galvanometer to measure each of the electric current, the electromotive force and the electrical resistance.

………………………………………………………………………………………………………………………………………………………………………….

Problems:

A coil of cross sectional area 0.2 m^2 is placed normal to a regular magnetic flux of density 04 Weber/m^2 . Calculate the magnetic flux which passes through this coil.(0.008 Wb)

A wire of 10 cm length, carrying a current 5 A, is placed in a magnetic field of 1 Tesla flux density. Calculate the force acting on the wire, when:

The wire is at right angles to the magnetic field. (0.5 N)

The angle between the wire and thefield is 45°. (0.356 N)

The wire is parallel to the magnetic flux lines. (0)

A straight wire of diameter 2 mm carries a current of 5A. Find the magnetic flux density at a distance of 0.2 m from the wire. (5×〖10〗^(-6) Tesla)

A circular loop of radius 0.1 m carries a current of 10 A. What is the magnetic flux density at its center? (the loop has one turn). (2π×〖10〗^(-5) Tesla)

What is the magnetic flux density at a point on the axis of a solenoid of length 50 cm carrying a current of 2A and has 4000 turns? (0.02 Tesla)

A rectangular loop (12×10 cm) of 50 turns, carrying a current of 3 A, is placed in a magnetic field of 0.4 Tesla flux density, such that the plane of the loop is parallel to the field. Calculate the torque acting on the loop. (0.72 Nm)

A galvanometer’s loop of 5×〖12 cm〗^2 and 600 turns is suspended in a magnetic field of 0.1 Tesla flux density. Calculate the current required to produce a torque of 1 Nm.

(2.78 A)

A loop of cross-sectional area 0.2 m^2 and 500 turns, carrying a current of 10 A is placed at 30° between the normal to its plane and a magnetic field of 0.25 Tesla flux density. Calculate the torque acting on the loop. (125 Nm)

The coil of an ammeter is capable of carrying current up to 40 mA. If the resistance of the coil is 0.5Ω, and it is desired to use the ammeter for measuring a current of 1 A,

What is the resistance value of the required shunt?

A galvanometer gives full scale deflection at current 0.02 A, and its terminal voltage is 5 V. What is the value of the multiplier resistance required to make it valid to measure potential difference up to 150 V? (7250 Ω)

A voltmeter reads up to 150 V at full scale deflection. If the resistance of its coil is 50 Ω and the current flowing 4×〖10〗^4 A. Calculate the resistance of the potential multiplier connected to the coil? (374950 Ω)

A galvanometer reads up to 5A and has a resistance of 0.1 Ω, If we went increase its reading 10 times, what is the value of the required shunt resistor? (0.0111Ω)

An ammeter has resistance 30Ω. Calculate the value of the required shunt resistor to (Decrease the sensitivity) to one third, and determine also the total resistance of the ammeter and the shunt resistor. (15 Ω, 10 Ω)

A galvanometer of resistance 54Ω, when connected to a shunt (a), the current flowing through the galvanometer is 0.1 of the total current. But if connected to a shunt (b), 0.12 of the total current flows through the galvanometer. Find the resistances of a and b. (6 Ω, 7.364 Ω)

A moving coil galvanometer of resistance 50 ohms gives full scale deflection at current 0.5A. How could it be converted to measure:

Potential difference up to 200V? (350 Ω in series)

Electric currents up to 2A? (16 2/3 Ω in parallel)

A milliammeter of resistance 5 Ω has a coil capable of carrying a current of 15 mA. It is desired to use it as an ohmmeter using an electric cell of 1.5 V having internal resistance 1 Ω. Calculate the required standard resistor, and calculate the external resistance needed to make the pointer deflect to 10mA? Calculate the current that flows through it when connected to an external resistor of 400? (94Ω, 50Ω, 3mA)

First Exam

Question One:

Write down the scientific term:

The magnetic torque acting on a coil carrying current placed parallel to magnetic flux density of 1 Tesla.

………………………………………………………………………………………………………………………………………………………………………….

A small resistance connected in parallel with the coil of the galvanometer to convert it to an ammeter.

………………………………………………………………………………………………………………………………………………………………………….

The scale deflection of the pointer of the galvanometer when unit current intensity passing through its coil.

…………………………………………………………………………………………………………………………………………………………………………

The magnetic flux density which exerts a force 1 N on a wire of length 1 m carrying current intensity 1 A placed perpendicular to the magnetic flux lines.

………………………………………………………………………………………………………………………………………………………………………….

Ability of the medium to pass magnetic field through it.

………………………………………………………………………………………………………………………………………………………………………….

First: Mention only ONE factor affecting on:

Magnetic flux density at a point along axis of solenoid carrying current.

………………………………………………………………………………………………………………………………………………………………………….

Type of mutual force between two parallel straight wires carrying currents.

………………………………………………………………………………………………………………………………………………………………………….

Magnetic dipole moment of a coil.

………………………………………………………………………………………………………………………………………………………………………….

Second: Compare between each of:

Sensitivity of galvanometer before and after converting it into ammeter (with respect to value).

………………………………………………………………………………………………………………………………………………………………………….

Galvanometer resistance before and after converting it into ammeter.

………………………………………………………………………………………………………………………………………………………………………….

Fleming's left hand rule and Right hand screw rule (with respect to their application).

………………………………………………………………………………………………………………………………………………………………………….

In the opposite figure:

A metallic loop and insulated conducting wire each carries a current and placed on the plane of paper, if the net magnetic flux density at the center of the loop equals zero. Calculate (π=3.14)

Distance between the wire and center of the loop.

Determine the direction of the current in the wire.

………………………………………………………………………………………………………………………………………………………………………….

Question Two:

Write down the mathematical formula:

Magnetic flux passing through ross-sectional area in terms of its flux density.

………………………………………………………………………………………………………………………………………………………………………….

Magnetic flux density at the center of circular coil carrying current.

………………………………………………………………………………………………………………………………………………………………………….

Sensitivity of galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

Calculating an unknown resistance by connecting with an ohmmeter of known resistance.

………………………………………………………………………………………………………………………………………………………………………….

Shunt resistance in the ammeter.

………………………………………………………………………………………………………………………………………………………………………….

First: What is the scientific idea of?

Converting a sensitive galvanometer into voltmeter.

………………………………………………………………………………………………………………………………………………………………………….

The operation of sensitive galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

Using ohmmeter for measuring resistance.

………………………………………………………………………………………………………………………………………………………………………….

Second: Mention the function of:

Standard resistance in the ohmmeter.

………………………………………………………………………………………………………………………………………………………………………….

Metallic cylinder inside the coil of galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

Spiral springs on the axis of galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

A battery its emf 14V and of negligible internal resistance connected to a circular coil of 50 turns and diameter 20cm. If the specific resistance of the wire is 7×〖10〗^(-7) Ω.m and radius of wire 1 mm. Calculate the torque acting on the coil when placed parallel to magnetic flux density of 0.5T.

………………………………………………………………………………………………………………………………………………………………………….

Question Three:

Choose the correct answer:

To determine the polarity of circular coil carrying current, the rule used is...……

Fleming's left hand

Fleming's right hand

Clockwise rule

Magnetic flux density at the axis of a solenoid increases with increasing its………..

Radius

Number of turns

Length

Magnetic field of electric current passing through a solenoid is similar to the field of the

U-shaped magnet

Bar magnet

Round shape magnet

Torque acting on a coil carrying electric current and placed in a magnetic field vanishes when the plane of coil is…………

Parallel to the field

Perpendicular to the field

Inclined at an acute angle

The direction of the force acting on a wire carrying electric current and placed perpendicular to the direction of the magnetic field is normal to............

The direction of current and parallel to the field.

The direction of current and the field.

The direction of field and parallel to the current.

First: When the following quantities equal zero?

The magnetic flux density at the center of two concentric metal loops carrying electric current in which the diameter of the first loop is double that of the second.

The magnetic flux density at a point between two parallel straight wires carrying an electric current.

The magnetic force acting on a wire carrying current and placed in a magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

Second: Find the slope of:

…………………………………………

…………………………….…………….

………………………………………..

Milli-ammeter of coil resistance 4 Ω and maximum current that can carry is 16mA, it is desired to convert it to an ohmmeter using electric cell of emf 1.5V and internal resistance 1.75 Ω.

Calculate:

Standard resistance.

The external resistance that makes the pointer deflects to 10 mA.

Current intensity passing when connected to external resistance of 300 Ω.

………………………………………………………………………………………………………………………………………………………………………….

Question Four:

Explain that:

A metallic wire is free to move when carrying current and placed perpendicular to the magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

The torque acting on a coil carrying current placed parallel to the magnetic field decreases until reaches to zero starting from the position parallel to the magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

When passing an electric current in a solenoid and straight wire free to move, placed along axis of solenoid, the wire doesn't move.

………………………………………………………………………………………………………………………………………………………………………….

Attraction between two parallel wires carrying currents in same directions.

………………………………………………………………………………………………………………………………………………………………………….

No neutral point between two parallel wires carrying currents.

………………………………………………………………………………………………………………………………………………………………………….

First: What are the results for?

Increasing the value of multiplier resistance connected to galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

Absence of variable resistance in the ohmmeter.

………………………………………………………………………………………………………………………………………………………………………….

Decreasing the shunt resistance connected to galvanometer.

………………………………………………………………………………………………………………………………………………………………………….

Second: Mention the case that each of the following could happen:

Repulsion between two parallel straight wires carrying current.

………………………………………………………………………………………………………………………………………………………………………….

Vanishing of magnetic flux density at the axis of solenoid carrying an electric current.

………………………………………………………………………………………………………………………………………………………………………….

A rectangular coil carrying current and placed inside magnetic field doesn't rotate.

………………………………………………………………………………………………………………………………………………………………………….

The following table represents the relation between magnetic flux density (B) of variable field and torque (τ) acting on a rectangular coil carrying current (I), its number of turns (N) and with cross-sectional area (A) and placed parallel to the magnetic field.

Magnetic flux density (B) (Tesla) 0.1 0.2 X 0.5 0.6 0.8

Torque (𝛕) (N.m) 20 40 80 100 Y 160

Draw the graph between torque (τ) on the vertical axis and the magnetic flux density (B) on the horizontal axis. From the graph Find:

Value of (X) & (Y).

Magnetic dipole moment.

Second Exam

Question One:

Write down the scientific term:

The magnetic flux passing normally through unit area surrounding a point.

………………………………………………………………………………………………………………………………………………………………………….

Large resistance is connected in series with the galvanometer coil to convert it to voltmeter.

………………………………………………………………………………………………………………………………………………………………………….

A measuring device is used to detect a very weak current in the electric circuit and measuring its intensity and determine its direction.

………………………………………………………………………………………………………………………………………………………………………….

A device used to measure the value of unknown resistance directly.

………………………………………………………………………………………………………………………………………………………………………….

Magnetic pole formed at one terminal of a solenoid if carrying current its direction is anti-clockwise.

………………………………………………………………………………………………………………………………………………………………………….

First: Mention only One factor affecting on:

The torque affecting on a coil carrying current placed inside a magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

Magnetic flux density at point of normal distance from straight wire carrying current.

………………………………………………………………………………………………………………………………………………………………………….

The value of the force affecting on a straight wire carrying current placed inside a magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

Second: Compare between each :

The position of the neutral point in case of two parallel straight wires and carrying different currents through them (with respect to direction of current through each).

Shunt resistance and multiplier resistance (with respect to the way of connection with galvanometer's coil).

Magnetic flux density at a point on the axis of solenoid carrying current (before and after displacing away its turns from each other).

Circular coil of diameter 10cm and its number of turns (N) carrying current (I) and produce magnetic field at its center. If we stretch the coil in the direction of its axis to produce a solenoid of same current intensity. Calculate the length of the solenoid which makes magnetic flux density at a point on its axis equals quarter the magnetic flux density at the center of the coil.

Question Two:

What will happen with mentioning the reason?

Passing AC current through a moving coil galvanometer (with respect to the deflection of its pointer).

………………………………………………………………………………………………………………………………………………………………………….

Putting a soft iron cylinder inside a solenoid carrying current (with respect to the magnetic flux density at a point on its axis).

Connecting an ammeter in parallel between the terminals of an ohmic resistance in a closed circuit (with respect to the effect on the potential difference between its terminals).

Passing a current in the straight wire placed perpendicular in uniform magnetic field (with respect to the direction of wire's motion).

Passing a direct current of high intensity through sensitive galvanometer (with respect to the possible damage).

First: Write down the mathematical formula:

Magnetic dipole moment of a coil.

………………………………………………………………………………………………………………………………………………………………………….

The mutual force between two parallel straight wires carrying different currents.

………………………………………………………………………………………………………………………………………………………………………….

The magnetic force affecting on a straight wire has length (L) and carrying current (I) placed in magnetic flux of density (B).

………………………………………………………………………………………………………………………………………………………………………….

Second: What is meant by?

The sensitivity of the galvanometer is 0.2 degree/μA.

The value of multiplier resistance = 700 Ω.

The magnetic dipole moment for a coil is 8 N.m/T.

Galvanometer of coil's resistance 5Ω and gives full scale deflection when the potential difference between its terminals is 0.1 volt. Calculate:

The maximum current can be measured if it was connected with shunt resistance 0.1Ω.

The value of multiplier resistance required to convert the galvanometer to voltmeter measuring maximum potential difference 5 volt.

Question Three:

Choose correct answer:

In the shown figure, (I_1) greater than (I_2) then the magnetic flux density in the middle distance between the two wires may be equals..............

(B_2-B_1)

(B_1-B_2)

(B_1+B_2)

The equivalent resistance of the voltmeter device equals.......

(R_s R_m)/(R_s 〖+R〗_m )

R_s R_m

R_g+R_m

Galvanometer of coil's resistance (R), so the shunt resistance which makes the sensitivity decreases to its one third is.........

R/2

R/3

If a resistance of 100Ω makes the pointer of ohmmeter deflects to half its scale, so the resistance which makes the ohmmeter deflects to quarter its scale is.........

300 Ω

200 Ω

100 Ω

Passing an electric current in a circular coil produces magnetic flux density at its center (B), when the current intensity is doubled and increasing the diameter of the coil to double without changing the number of turns, so the magnetic flux density in the center of the coil equals.........

2 B

B/2

First: When does the physical quantity equal zero?

The magnetic force affecting on straight wire placed inside magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

The electric current intensity passing through the ohmmeter circuit.

………………………………………………………………………………………………………………………………………………………………………….

The magnitude of pointer's deflection from its zero position in the ohmmeter device.

………………………………………………………………………………………………………………………………………………………………………….

Second:

Prove that the torque affecting on a coil has a number of turns (N) and passing through it an electric current with intensity (I) and placed parallel to the magnetic field (B) can be determined from the relation umber of turns (N) and passing through it an electric current with intensity (I) and placed parallel to the magnetic field (B) can be determined from the relation τ=BIAN

If the resistance of the micro-ammeter device is 250Ω and the maximum current can be measured is 400𝛍A, connected in series with it a standard resistance 3000Ω, variable resistance 6565Ω, and a battery with emf 1.5V with negligible internal resistance, to use it as an ohmmeter for measuring unknown resistance. Calculate:

The value of resistance must be taken from variable resistance in order that maximum deflection is obtained.

The value of external resistance connected to make the pointer deflects to half its scale.

Question Four:

Give reason for:

The permanent magnetic poles in the galvanometer are concave.

The scale of ammeter is uniform but the scale of ohmmeter is non-uniform.

Fixing two spiral spring at the axis of the coil of the moving coil galvanometer.

Using an electric source with constant emf in the ohmmeter.

The ammeter is connected in series but the voltmeter is connected in parallel in the electric circuits.

First: What are the results of?

Using an ammeter with full scale deflection 10 Ampere to measure current intensity of 0.5 mA.

………………………………………………………………………………………………………………………………………………………………………….

Putting a bar of soft iron core inside a solenoid carrying direct current.

………………………………………………………………………………………………………………………………………………………………………….

Passing an electric current in a rectangular coil placed parallel to magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

Second: How can you obtain?

The maximum force acting on straight a wire carrying current and placed in a magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

Vanishingthe magnetic flux density at a point between two straight wires carrying current in the same direction having a distance from one of them equals quarter the distance between the two wires.

Decreasing the sensitivity of the galvanometer to its half value.

A metallic wire of length 1m carrying current 10 A placed in magnetic field its density (B), this table shows the relation between the force (F) affecting on this wire and (Sin θ) the angle between the direction of the field and the wire.

F (N) 0.2 0.4 0.6 0.8 1 1.2

Sin θ 0.1 0.2 0.3 0.4 0.5 0.6

Plot the relation between the force affecting on the wire (F) in Newton on vertical axis (Y-axis) and the (Sin θ) on horizontal axis (X-axis). From the graph Find:

The value of the force affecting on the wire when it placed perpendicular to the magnetic field.

Magnetic flux density acting on the wire.

THIRD: EXAMS ON Chapter (3)

MAGNETIC EFFECT OF ELECTRIC CURRENT

Put (√) against the right answer:

The pointer of a galvanometer whose terminals are connected to a solenoid coil will be deflected if one withdraws the magnet quickly from the coil because:

The number of the coil turns is very large.

The coil intercepts the lines of the magnetic flux.

The number of the turns of the coil is small.

The number of turns of the coil is suitable.

The needle of the galvanometer whose terminals are connected to a solenoidal coil deflects on the withdrawal of the magnet in a direction opposite to that which occurs on plunging the magnet into the coil because:

An induced current is generated in a direction opposite to that on plunging the magnet.

An electric current is generated.

The number of the lines of magnetic flux decreases.

The number of the lines of the magnetic flux changes.

The number of flux lines remains constant.

The emf induced in a coil on plunging a magnet into or withdrawing it out of a coil differs according to the difference in:

[The intensity of the current – the length of the wire – the number of the lines of flux].

[Magnet strength – the velocity with which the magnet moves – the number of turns of the coil].

[The cross sectional area of the coil – the mass of unit length – the material from which the wire is made].

[The length of the wire – the number of turns – the type of the magnet].

[The magnetic flux density – time – the intensity of the current].

A current passes in the primary coil, then this coil is plunged into a secondry coil whose terminals are connected to a galvanometer. The deflection of its needle will be in a direction:

Opposite to the current in the primary coil.

Points to zero reading.

Same as the current in the primary coil.

Variable

Opening the primary circuit while the primary coil is inside the secondary one, leads to the generation of:

An induced forward current.

An electric field.

An AC current.

A magnetic field.

The slow rate of growth of the current in the solenoidal coil is due to the:

Production of forward current.

Production of a magnetic field.

Production of a back induced current opposing (resisting) the original one.

Production of a magnetic flux.

Production of an electric field.

The ohmic resistors are made of double wound wires:

to decrease the resistance of the wire.

to increase the resistance of the wire.

to avoid self-induction.

to eliminate the resistance of the wire.

to facilitate the connection process.

The direction of the current produced in the dynamo coil can be determined using:

Fleming’s left hand rule.

Lenz’s rule.

Fleming’s right hand rule.

The rate with which the coil intercepts the lines of magnetic field in the dynamo is maximum when:

The plane of the coil is perpendicular to the flux lines.

The plane of the coil is inclined to the lines by an angle 30°

The face area of the coil is minimum.

The face area of the coil is maximum.

The plane of the coil is parallel to the lines of the magnetic flux.

The intensity of current in the two coils of the transformer is:

Directly proportional to the number of the turns.

Inversely proportional to the number of the turns.

Depending on the substance of the wire.

Depending on the temperature of the air (ambient temperature).

The power of an electric motor to rotate increases on using:

Larger number of turns.

Several coils with angles between their planes.

Several magnets.

An insulated copper wire.

A current rectifier.

The ratio between the electric energy in the secondary to that in the primary is called:

The lost energy.

The given energy.

The efficiency of the transformer.

The working strength of the transformer.

The gained energy.

Define the following:

Electromagnetic induction.

Faraday’s law of induction.

Lenz’s rule.

Fleming’s right hand rule.

Mutual induction between two coils

Measuring unit of the mutual inductance.

Self-induction of a coil.

Coefficient of self-induction.

The henry.

The induction coil.

The AC current.

The dynamo.

The electric motor.

The transformer.

The efficiency of the transformer.

The back emf in the motor.

Essay Questions:

What are the factors on which the emf induced in a conductor depends? Mention the relation between the emf, and such factors.

State Faraday’s law of the emf induced in a coil, then show how to verify this practically?

………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………….

What is meant by mutual induction between two coils? And what is meant by the coefficient of mutual induction? How – using the mutual induction – one can verify Lenz’s rule?

If a current passes through a coil, deduce an equation relating the induced emf in the coil and the rate of change of the current in the coil. From this, deduce a definition for the coefficient of self-induction and the Henry.

When does the emf induced in a coil become maximum? And when does it become zero?

Explain an experiment to show the conversion of the mechanical energy into electrical energy, and another experiment to show the opposite conversion. Then, state the rule used to define the direction of the current in the first case and the direction of motion in the second case.

Deduce the relation by which one can evaluate the instantaneous emf induced in an AC generator?

What are the modifications introduced to the AC generator to render it a unidirectional generator?

Describe the structure of the electric transformer? What are the factors which lower such efficiency and how to deal with them?

What is meant by the efficiency of the transformer? What are the factors which lower such efficiency and how to deal with them?

Draw a labeled diagram showing the structure of the motor and explain its operation.

Give reasons:

The core of an electric transformer is made of thin sheets insulated from each other.

A bar of soft iron will not be magnetized if a double wound wire carrying a current is wound around it.

A wire free to move in a magnetic field moves when a current passes through it.

The transformer is not suitable to convert DC voltage.

The electric motor rotates with uniform velocity.

The induced current dies out in a straight wire faster than in a coil with air core, and in a coil with air corenfaster than in a coil wound around an iron core.

The metallic cylinder used to obtain a unidirectional current in the dynamo is split into two halves completely insulated from each other.

Drills:

A coil of 80 turns, and cross-sectional area 0.2 m^2 is suspended in a perpendicular position to a uniform magnetic field. The average induced emf is 2 V when it rotates 1/4 revolution through 0.5 s. Find the magnetic flux density. (0.0625T)

If the magnetic flux density between the two poles of the magnet of a dynamo is 0.7 Tesla, and the length of its coil is 0.4 m, find the velocity of motion in such a field to obtain an induced emf in the wire equal to 1 V. (3.57 m/s)

A coil of a dynamo consists of 800 turns each of face area 0.25 m^2. It rotates at a rate of 600 revolutions per minute, in a field of magnetic flux density 0.3 Tesla. Calculate the induced emf when the angle made between the normal to the coil and the magnetic flux is 30° (1885v)

A rod of copper of length 30 cm moves with at velocity 0.5 m/s in a perpendicular direction to a magnetic field of density 0.8 Tesla. Calculate the emf induced in such a rod. (0.12v)

An antenna of length one meter fixed in a motor car, which moves at velocity 80km/hour in a direction perpendicular to the horizontal component of the Earth’s magnetic field. An emf of 4×〖10〗^(-4) V is induced in the antenna. In such a case, calculate the magnetic flux density of the considered horizontal field. (18×〖10〗^(-6) T)

Calculate the coefficient of self-induction for a coil in which an emf of 10 V is induced if the passing current changes at a rate of 40 A/s (0.25 Henry)

The mutual induction between two faces of opposite coils is 0.1 Henry and the intensity of current in one of them is 4 A. If this intensity drops to zero in 0.01s, find the emf induced in the other coil. (40 V)

A rectangular coil of dimensions 0.4m × 0.2m and of 100 turns rotates with a uniform velocity 500 revolutions per minute in a uniform field of magnetic flux density 0.1 Tesla. The axis of rotation in the plane of the coil is perpendicular to the field. Calculate the emf induced in the coil. (41.89 V)

A step-down transformer of efficiency 90% has a primary coil voltage of 200 V and that of the secondary is 9 V. If the intensity of the electric current in the primary is 0.5 A, and the number of turns of the secondary is 90 turns, what is the intensity of the current of the secondary coil, and what is the number of turns of the primary?

(10A, 1800 turns)

A step-down transformer connected to an AC power source of 2500 V gives a current of 80 A. The ratio between the number of turns of the primary and the secondary coils is 20:1 Assuming that its efficiency is 80%, find the emf induced across the two terminals of the secondary, and find also the current in the primary coil. (100V , 4A)

First Exam

Question One:

Choose the correct answer:

The average induced emf generated in a coil when it rotates around its axis 〖180〗^° starting from the perpendicular position on the magnetic flux lines = ……..

(Zero-2NAB/∆t- NAB/∆t)

While the average induced emf generated in the coil when it rotates around its axis 〖180〗^° starting from the parallel position on the magnetic flux lines = ……..

(Zero-2NAB/∆t- NAB/∆t)

By increasing the flux lines that cuts a secondary coil, a/an (Forward – backward – alternate) induced emf is generated in it.

While by decreasing the flux lines that cuts the coil, a/an (Forward – backward – alternate) induced emf is generated in it.

The direction of the induced emf generated in an induction coil is determined by using ……… (Fleming’s right hand – Lenz - Fleming’s left hand) rule.

While the direction of the induced emf generated in a straight wire moving perpendicular to magnetic flux lines is determined by using ……… (Fleming’s right hand – Lenz - Fleming’s left hand) rule.

The electric transformer doesn’t work when the current passing through its primary coil is …..

Unidirectional of variable intensity

Alternating current.

Unidirectional of constant intensity.

The current generated in the dynamo coil that connected a commutator is …… (Alternating current – Unidirectional current - variable intensity current)

While in the external circuit of the dynamo is ……

((Alternating current – Unidirectional current - variable intensity current)

First: Prove that the induced emf generated between the terminals of a straight wire moving perpendicular to a uniform magnetic field is determined by the relation:emf=-Blv

Second: Write the mathematical relation used to calculate each of the following:

The induced emf generated in a secondary coil when the electric current intensity in the primary coil that is near to it varies.

………………………………………………………………………………………………………………………………………………………………………….

The efficiency of the electric transformer.

………………………………………………………………………………………………………………………………………………………………………….

The induced emf generated in a straight wire moving perpendicular to a uniform magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

An electric transformer the ratio between the number of turns of its two coils is 1 : 5 is used to transfer an electric power of 100 KW with a potential difference of 200 Volts from an electric power station to the regions of distribution. Find the efficiency of transfer if the resistance of the transfer wires is 4 Ω.

Question Two:

What are the results for:

The two halves of the isolated metallic cylinder fixed to the coil of the motor are replaced by two metal rings.

Connecting the terminals of the primary coil in the electric transformer to DC source.

There is a high potential difference between the terminals of the fluorescent lamp.

The flow of an electric current in a coil made of double wound wires.

………………………………………………………………………………………………………………………………………………………………………….

An induced emf is generated in the coil of the motor during its rotation between the poles of a magnet.

First : Mention the factors affecting (Two only):

The coefficient of self-induction of a coil.

The maximum induced emf generated in the dynamo coil.

The efficiency of the electric transformer.

Second: What is meant by …..?

The effective emf of alternating current = 15 V

Coefficient of self-induction of a coil = 0.01 H.

The efficiency of the electric transformer = 85 %

A rectangular coil, its face area is 70 〖cm〗^2, rotates about its axis in a magnetic field of flux density 1 tesla such that it makes 300 rotations in half a minute. If the number of its turns was 100 turns, calculate :

The maximum emf.

The effective emf.

The time taken from the start of rotation from the perpendicular position till the emf reaches 22 V.

The time taken from the start of rotation from the perpendicular position till the emf reaches -22 V.

Question Three:

Write the scientific term:

The induced electromotive force generated in one of the two coils when the electric current intensity in the other coil changes in the rate of 1 Ampere every second.

………………………………………………………………………………………………………………………………………………………………………….

The induced current must be in a direction such as to oppose the change producing it.

………………………………………………………………………………………………………………………………………………………………………….

A rule used to determine the direction of the induced electric current in a straight wire moving perpendicular to a magnetic flux.

………………………………………………………………………………………………………………………………………………………………………….

An induced electric current generated in a metallic piece due to its exposure to a variable magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

The transformer in which there is no loss in power between its coils.

………………………………………………………………………………………………………………………………………………………………………….

First: Give reasons:

Using a group of coils separated by small equal angles in the electric motor.

The wrought iron core in the electric motor is made of thin sheets isolated from each other.

Using step up transformers at power stations.

Second: Mention the physical quantities measured in the following units and its equivalent unit

Wb.〖sec〗^(-1)

………………………………………………………………………………………………………………………………………………………………………….

V.s.A^(-1)

………………………………………………………………………………………………………………………………………………………………………….

V.s

………………………………………………………………………………………………………………………………………………………………………….

In the opposite figure:

An electric current of intensity 2 A passes in coil (A) produces magnetic flux 2.5×〖10〗^(-4) Wb passes through the coil (A) and 1.8×〖10〗^(-4) Wb through the coil (B). Calculate:

The coefficient of self-induction of coil (A).

The coefficient of mutual induction between (A) , (B).

The average induced emf generated in coil (B) when the current in coil (A) vanishes within 0.03 s.

Question Four:

Compare between:

The reason for the presence of more than one coil in each of the DC dynamo and the electric motor.

The reason for the presence of the two halves of the split metallic cylinder in the DC dynamo and the electric motor.

Fleming’s right hand rule and Lenz’s rule (in terms of usage).

The electric transformer and the electric motor (in terms of the scientific base).

The step up transformer and the step down transformer (in terms of the number of turns in the primary coil and the secondary coil).

First: In the opposite figure:

What happens instantaneously to the brightness of the lamp:

At the moment of switching the key off.

Increasing the resistance R.

Second: An electric transformer of efficiency 80%. If the number of turns of its secondary coil is less than that of its primary coil, and the turns of its secondary coil are thicker than the turns of its primary coils.

Is it a step down or a step up transformer ?

Explain why the turns of its secondary coil are made to be thicker than the turns of its primary coils.

………………………………………………………………………………………………………………………………………………………………………….

The opposite figure represents the change in the electric current which is generated from an AC dynamo with time, find:

The angular velocity of the dynamo coil.

The effective value of that current.

Explain how you can obtain the currents represented by figures (a) and (b).

………………………………………………………………………………………………………………………………………………………………………….

Second Exam

Question One:

Choose the correct answer:

If the maximum electric current intensity generated in the dynamo coil is (I), then the average current intensity during half cycle from the zero position is ……..

(Zero-I/2- (2 I)/π-I/√2)

When the electric current intensity passing through a coil changes, an induced current is generated in the coil due to …………………

(The self-induction – The mutual induction – The eddy currents – The torque)

In the ideal step up transformer, ………

(The current increases – The power increases – The frequency increases – The current decreases).

A rectangular coil starts its rotation around its axis PQ between the poles of a magnet as shown in the figure. Which of the following graphs represents the change in the induced eme for one complete cycle ? …..

When the angle between the plane of the dynamo coil and the direction of the magnetic flux is 〖60〗^°, then the induced emf becomes ……..

√3/2of the maximum value.

1/2of the maximum value.

equal to the maximum value.

equal to the effective value.

First: What are the factors affecting each of the following..?

The induced emf in Faraday’s experiment.

The intensity of the eddy currents.

The effective value of induced emf in the dynamo coil.

Second: An insulated coil wrapped around a rod of wrought iron, mention what happens to the rod in each of the following case:

When DC current passes in the coil.

When AC current passes in the coil.

The coil wire is double coiled and an AC current passes through it.

A coil of 100 turns and its section area is 200 cm2 is placed such that it makes an angle 〖60〗^° with the direction of a uniform magnetic flux of density √3 T. Calculate:

The magnetic flux passing through the coil.

The torque acting on the coil when an electric current of intensity 2 A passes through it.

The induced emf when the current in the coil is cut off within 0.1 s

Question Two:

Write the scientific term :

The induced emf generated in a coil by electromagnetic induction is directly proportional to the time rate by which the conductor intercepts the lines of the magnetic flux lines and is also proportional to the number of turns of the coil.

………………………………………………………………………………………………………………………………………………………………………….

A device used in transferring the electric energy from the electric power stations to places where it can be used without loss in energy.

………………………………………………………………………………………………………………………………………………………………………….

A device used to convert a part of the mechanical energy done to move the coil in the magnetic field into electric energy.

………………………………………………………………………………………………………………………………………………………………………….

The conversion of the alternating current into a unidirectional current of almost constant intensity.

………………………………………………………………………………………………………………………………………………………………………….

A rule is used to determine the direction of the torque acting on the coil of the electric motor.

………………………………………………………………………………………………………………………………………………………………………….

First: In the opposite figure: What happens to the intensity of the bulb illumination when:

Approaching the magnet to the coil.

The magnet is placed for a period of time inside the magnet.

Moving the magnet away from the coil.

Second : Prove that: The induced emf generated in a coil of coefficient of self-induction L due to the change of the current in it by a rate of ∆I/Δt is given from the relation :

emf=-L × ∆I/Δt

An electric transformer is used to decrease the electric potential from 2400 V to 120 V , and produces an electric power of 13.5 KW. If the number of turns of primary coil is 4000 turns and the efficiency of the electric transformer is 90% , calculate :

The number of turns of the secondary coil.

The current intensity passes in the each of the primary coil and the secondary coil.

Question Three:

Observe the electric circuit shown in the figure, then answer the following:

What is the name of the electric device shown in the figure?

Write the name of the components labeled by (a) and (b).

What is the function of the part (b)?

Determine the direction of the coil rotation.

What happens if the component (b) is replaced by two metal rings each ring is connected to one of the coil terminals?

First: Mention one use for each of the following:

The induction furnaces.

………………………………………………………………………………………………………………………………………………………………………….

Fleming’s right hand rule.

………………………………………………………………………………………………………………………………………………………………………….

The back induced emf in the electric motor.

………………………………………………………………………………………………………………………………………………………………………….

Second: A coil of area 0.04 m2 and number of turns 150 turns, its plane is perpendicular to a magnetic field that changes based on the graph illustrated in the opposite figure.

In every stage of change in the graph, calculate the average induced emf in the coil.

A rectangular coil of 100 turns, with dimensions 20 cm and 10 cm rotates with a uniform speed of 3000 revolutions per minute in a uniform magnetic field of magnetic flux density 0.28 T, find:

The maximum induced emf.

The induced emf after 5 ms from the zero position.

The induced emf when the coil makes 〖30〗^° from the previous position in question number (2).

The effective value of the induced emf.

Question Four:

When does the following values equal zero:

The induced emf generated in a straight wire moving in a magnetic field.

………………………………………………………………………………………………………………………………………………………………………….

The magnetic flux passing through the dynamo coil.

………………………………………………………………………………………………………………………………………………………………………….

The instantaneous emf in the dynamo coil during its rotation.

………………………………………………………………………………………………………………………………………………………………………….

The average induced emf in the dynamo coil during its rotation.

………………………………………………………………………………………………………………………………………………………………………….

The induced emf in a solenoid at the moment of closing its circuit.

………………………………………………………………………………………………………………………………………………………………………….

First: Compare between each of the following:

The step up and the step down transformer (Concerning the value of current in each of the primary and the secondary coil).

The alternating current and the DC current (Concerning the direction of flow).

The average induced emf in the coil of AC dynamo within quarter cycle and within half cycle starting from the zero position (Concerning the used law).

First: In the opposite figure: What happens to the glow of the lamp when ….?

Inserting a rod of wrought iron in each of the two coils.

Increasing the rotation frequency of the dynamo coil.

Increasing the number of turns of coil number (2)

An ideal electric transformer, the number of turns of its primary coil is 250 turns and the number of turns of its secondary coil (Ns) is variable. If the transformer is used to obtain different potential differences (Vs), and the relation is illustrated in the below table:

V_s (Volt) 48 72 96 120 144

N_s 50 75 100 125 150

Draw V_s on the Y-axis and N_s on the X-axis, from the drawing find:

The slope of the line.

The voltage of the source connected to the primary coil.

The power produced from the secondary coil when the number of its turns is 200 and the resistance of its circuit is 75 Ω.

Third Exam

Question One:

Choose the correct answer:

In the step up transformer, the secondary coil has ………. Greater than the primary coil.

(Power – Current intensity – Potential difference – Frequency)

When the dynamo coil generates an emf equals half the maximum induced emf, then the plane of the coil is inclined by an angle ……… on the direction of magnetic flux lines.

(〖30〗^° – 〖45〗^° – 〖60〗^° – 〖90〗^°)

When the effective value of induced emf by the dynamo coil is 50 volt then the average emf within 1/4 cycle equals ……. Volt.

(45 – 63 – 70.7 – 141.42)

In the dynamo coil, If the required period by the alternating current to reach from zero to half the value of maximum emf is (t), then the required time to reach the maximum value is …..

(t – 2t – 3t – 4t)

In the opposite figure:

If the number of turns of the primary coil is 4 turns and that of the secondary coil is 8 turns. What is the potential difference between the terminals of the resistor (R) ?

(Zero – 12.5 V – 25 V – 50 V)

First: Mention the physical quantities measured in the following units and its equivalent unit

T.m^2/s.

………………………………………………………………………………………………………………………………………………………………………….

V.s/m^2.

………………………………………………………………………………………………………………………………………………………………………….

V.s/A

………………………………………………………………………………………………………………………………………………………………………….

Second: Mention one factor that affects each of the following:

The direction of the generated current in the dynamo coil.

The direction of movement of the electric motor’s coil.

The power of the electric motor.

AC dynamo its coil is formed of 420 turns, the area of its face is 3×〖10〗^(-3) m^2. It rotates in a magnetic field of flux density 0.5 T. If the coil started its rotation from the perpendicular position to the flux lines and reached to the maximum induced emf after 1/200 sec. Find :

The maximum induced emf.

The time required to reach half the maximum value of emf.

The effective value of the generated induced emf.

Question Two:

What happens when …?

The coil of the electric motor becomes perpendicular to the direction of the magnetic flux lines during its rotation.

………………………………………………………………………………………………………………………………………………………………………….

The plane of the dynamo coil is perpendicular to the magnetic flux lines (Concerning the rate by which the dynamo coil cuts the magnetic flux lines).

………………………………………………………………………………………………………………………………………………………………………….

Displacing the brushes of the unidirectional dynamo by 〖90〗^°such that the line between them becomes perpendicular to the magnetic flux lines, without any other change in the dynamo structure.

First: Compare between:

Lenz’s rule and Fleming’s right hand rule (In terms of usage).

The dynamo and the electric motor (In terms of the scientific base).

Transferring the electric energy from power stations: Once directly, and by using electric transformers another time.

Second: Figure (A) shows a coil rotating between the poles of a magnet in a dynamo, and its ends T1 , T2 are connected to an external circuit.

While figure (B) shows the change in the induced emf with time for the same dynamo:

Which of the points A , B or C shown in figure (2) represents the induced emf in the coil when it passes by the perpendicular position to the flux lines ? Explain your answer.

Find the time taken by the coil to change the induced emf from 45 V to 22.5 V for the first time.

If the speed of rotation of the coil increases, what is the effect of that on:

The maximum value of the induced emf.

The periodic time.

The ratio between the number of turns for the two coils in an ideal step up transformer is 1 : 100. If the primary coil is connected to AC source of 200 Volts. Calculate :

The induced emf in the secondary coil.

The ratio between the current value in the primary coil to that in the secondary coil.

The power produced in the secondary coil if the current intensity passing through it is 2 Amperes.

What happens if the AC source is replaced by DC source having the emf as that of the AC source?

Question Three:

What is the role of each of the following:

The siliconic wrought iron core in the electric transformer.

………………………………………………………………………………………………………………………………………………………………………….

The two carbon brushes in the AC dynamo and the electric motor.

………………………………………………………………………………………………………………………………………………………………………….

The electric transformer at the electric power stations.

The dynamo.

………………………………………………………………………………………………………………………………………………………………………….

The high voltage between the terminals of the fluorescent lamp.

First: In the opposite figure:

The two metal rods (A) and (B) can slide on two parallel wires perpendicular to a uniform magnetic field.

If the magnetic field started to decrease gradually, describe the motion of the two conductors, and explain your answer.

Second: In the step up voltage electric transformer: The potential between the terminals of the secondary coil is greater than the potential between the terminals of the primary coil.

Does this violate the law of energy conservation? Explain your answer.

A small circular loop consists of one turn of radius 5 cm and resistance 10-3Ω is placed at the center of a big loop consists of one turn of radius 50 cm. A variable current changes uniformly from 0 to 8 A within 10-6 s passes through the big loop. Calculate the electric current generated in the small loop within the same period.

Question Four:

What is the scientific idea of each of the following:

The induction furnaces.

………………………………………………………………………………………………………………………………………………………………………….

The electric motor.

………………………………………………………………………………………………………………………………………………………………………….

The electric generator.

………………………………………………………………………………………………………………………………………………………………………….

The electric transformer.

………………………………………………………………………………………………………………………………………………………………………….

The fluorescent lamp.

………………………………………………………………………………………………………………………………………………………………………….

First:In the opposite figure and at the moment of closing the circuit of the primary coil.

Draw the current directions and the magnetic flux (the magnetic poles) in the primary coil, with mentioning the used rule.

Draw the current directions and the magnetic flux (the magnetic poles) in the secondary coil, with mentioning the used rule.

Second: Describe the position of the dynamo coil with respect to the magnetic flux when the instantaneous current intensity is:

Maximum value.

1/2the maximum value.

Equal to the effective value.

In the opposite figure:

A circular coil consists of 200 turns is placed horizontally. The north pole of a magnet moves perpendicularly to the coil so the flux through the coil changes from 2.5×〖10〗^(-3) Wb to 8.5×〖10〗^(-3) Wb within 0.4 s. Calculate:

The average induced emf generated in the coil.

Show by drawing the direction of the induced electric current in the coil, and mention the used rule.

What happens to the generated emf if the magnet fell faster through the coil ? And why?

………………………………………………………………………………………………………………………………………………………………………….

FOURTH: EXAMS ON Chapter (3)

ALTERNATING CURRENT CIRCUITS

What is meant by each of the following…..?

The inductive reactance – The capacitive reactance – impedance – The oscillator circuit

Mention the factors that affect each of:

The inductive reactance

The capacitive reactance

Frequency of an oscillator circuit.

The impedance

How is the total capacitated for a number of capacitors connected together:

In series

In parallel.

Describe the construction of the oscillator circuit and explain its operation.

Describe the construction of the turned circuit and explain its operation in the radio receiver device.

Find the total capacitance of two capacitors of capacitance 24 and 48 microfarad connected together:

In series

In parallel

AC current of frequency 50 Hz passes through a resistor 12 Ω and an inductor of inductance 7/440 Henry connected together in series. Find impedance of the circuit.

(13 Ω)

Calculate the value of current passing through an inductive coil of self-inductance 7/275 Henryand ohmic resistance 6 Ω if the coil is connected to:

A direct power supply of emf 6 Volt and negligible internal resistance.

An alternating power supply of emf 6 Volt and frequency 50 Hz. (0.6 A, 1 A)

Three identical capacitors, of capacitance 14 microfarad each, are connected in parallel then to a power supply of frequency 50 Hz. Calculate the total capacitive reactance.

A resistor of 6 Ω, a capacitor of capacitive reactance 800 Ω and a coil of self-inductance 0.28 Henry are connected together in series to an AC power supply of voltage 20 V and frequency 50 Hz. Find:

The potential difference between the capacitor plates.

The phase angle between the total voltage and current.

The maximum of the current value that can be reached in the circuit. (160V, 53°, 2.8A)

A tuned circuit in a radio receiver consists of an inductive coil of inductance 10 millinery, a resistance 50 Ω and a capacitor of variable capacitance. Wireless waves of frequency 980 kHz hit the antenna and generate a voltage 〖10〗^(-4) Volt across the circuit. Find the capacitor capacitance and the current value at resonance.

(2.635×〖10〗^(-12) F,2×〖10〗^(-6) A)

A series circuit consists of a coil of inductive reactance 250 Ω, a resistance 100 Ω, a capacitor of variable capacitance and AC power supply of electromotive force 200 Volt and frequency 1000/44 Hz. Given that the current through the circuit reached its maximum value, find:

The capacitive reactance that caused the current to reach its maximum.

The potential difference between the terminals of the coil and the capacitor plates in this case. (28×〖10〗^(-6) F,500 V)

The circuit illustrated in figure contains an AC supply of frequency 50 Hz and electromotive force 220 Volt, a capacitor of capacitance 4 microfarad and an inductor of inductance 2.53 Henry. Find:

The capacitive reactance.

The inductive reactance.

What happens to the glowing of the electric bulb when only K_1 is turned on?

Find the impedance.

What happens to the glowing of the electric bulb when only K_2 is turned on?

Find the impedance.

What happens to the glowing of the electric bulb when both K_1 and K_2 are turned on?

Find the impedance. (795.4 Ω, 795.4 Ω, 1128 Ω ,1128 Ω)

First Exam

Question One:

Choose the correct answer:

This figure represents the circuit at resonance, when we remove the iron core from the coil, so the reading of the hot wire ammeter..............

Decreases

Increases

Remains constant

Becomes zero

If the circuit shown at resonance, then the frequency of the source is........ (𝛑 = 3.14)

2.251 KHz

444.3 MHz

71.2 KHz

7.12 MHz

In RLC Circuit, which of these statements is correct?

The reactance is equal the resistance at resonance

The impedance equals self-inductance at resonance

The current intensity is maximum at resonance

The impedance is maximum at resonance

Which of these figures represents resonance in RLC circuit?

When RLC circuit is at resonance, the impedance is...............and equals......... of the circuit.

Minimum value, resistance

Maximum value, resistance

Minimum value, reactance

Maximum value, reactance

First: Mention TWO factors:

Inductive reactance of a coil.

Capacitive reactance of a capacitor.

Resonance frequency in RLC circuit.

Second: Compare between:

Moving coil ammeter and hot wire ammeter (with respect to their scale division).

Inductive reactance and capacitive reactance (with respect to the effect of increasing the frequency).

Hot wire ammeter connected with inductive coil with zero ohmic resistance and current source in a closed circuit when passing AC and DC currents having the same emf (with respect to the reading of hot wire ammeter).

Tuning circuit consists of a capacitor of capacitance (C) mF and inductive coil of self-inductance (L) mH, this circuit receive waves its frequency 600 KHz, if we replace the coil by another one of inductance (3L) mH, and the capacitor with another one has (3C) mF. Find the frequency of the wave that can be received.

Question Two:

What is the scientific idea:

Hot wire ammeter.

………………………………………………………………………………………………………………………………………………………………………….

Oscillating circuit.

………………………………………………………………………………………………………………………………………………………………………….

Resonance circuit.

………………………………………………………………………………………………………………………………………………………………………….

The capacitor.

………………………………………………………………………………………………………………………………………………………………………….

Using platinum-iridium wire in the hot wire ammeter.

………………………………………………………………………………………………………………………………………………………………………….

First: Write down the mathematical formula:

The current frequency at resonance circuit.

………………………………………………………………………………………………………………………………………………………………………….

The impedance in RLC circuit.

………………………………………………………………………………………………………………………………………………………………………….

The total capacitive reactance for three capacitors connected in series.

………………………………………………………………………………………………………………………………………………………………………….

Second: What is meant by?

The current frequency used in houses = 50 Hz.

………………………………………………………………………………………………………………………………………………………………………….

The capacitor capacitance is 16 μF.

The inductive reactance of a coil = 160 Ω.

………………………………………………………………………………………………………………………………………………………………………….

A coil is connected to a DC source of emf 12 volts. A current of 1 Ampere flows through the circuit, when this source is replaced by an AC source (12 V – 50 Hz) a current of 0.6 Ampere flows in the circuit. When a capacitor is connected in series with the coil, the current intensity becomes 1 Ampere again Calculate: (π = 22/7).

The self-induction coefficient of a coil.

The capacitor capacitance.

The phase angle between the total voltage and the current intensity.

Question Three:

Write down the scientific term:

A device measures both AC and DC.

………………………………………………………………………………………………………………………………………………………………………….

An electric component is used to store the electric energy as charges, and electric fields are formed between its two plates.

………………………………………………………………………………………………………………………………………………………………………….

Electric circuit consists of inductive coil and capacitor with variable capacitance is used in wireless receiving circuits.

………………………………………………………………………………………………………………………………………………………………………….

Electric circuit consists of inductive coil and capacitor, where the energy in the capacitor stored as an electric field and is converted to magnetic field in the coil.

………………………………………………………………………………………………………………………………………………………………………….

The opposition to the flow of the AC current through a coil due to its self-inductance.

………………………………………………………………………………………………………………………………………………………………………….

First: Prove that the frequency at resonance is given from the relation f=1/(2π√LC).

Second: When these values equal zero?

The phase angle between the total voltage and the current in RLC circuit.

………………………………………………………………………………………………………………………………………………………………………….

The inductive reactance for a coil.

………………………………………………………………………………………………………………………………………………………………………….

Capacitive reactance of a capacitor of constant capacitance connected with AC source.

………………………………………………………………………………………………………………………………………………………………………….

AC source (220 V – 50 Hz) connected in series with resistance 8 ohm, inductive coil of inductance 0.1 H and a capacitor of capacitive reactance 25.4 ohm. Find: (𝛑 = 3.14)

The inductive reactance of the coil.

The current intensity passing in the circuit.

The potential difference between the terminals of each of resistance, coil and capacitor.

How can we modify in the circuit to obtain the maximum current? Find its value.

Question Four:

Give reason for:

At very high frequencies, we can consider the circuit which has an inductive coil as open circuit.

The electric which has a capacitor of a constant capacitance is considered as a closed circuit when the frequency is increased.

The scale of hot wire ammeter is non-uniform.

At resonance the current intensity is maximum and the impedance is minimum.

………………………………………………………………………………………………………………………………………………………………………….

The current decays after certain time in the oscillating circuit.

First: What will happen for?

Inserting a soft iron core inside a solenoid (with respect to the inductive reactance).

Connecting inductive coil with ohmic resistance connected with the terminals of an AC source (with respect to the phase angle between (V) and (I).

Connecting a battery with coil and capacitor in series (with respect to the electric current passing through them).

Second: Explain how to obtain?

The wire of the hot wire ammeter does not be affected by the atmospheric temperature.

Calibrating (scaling) the hot wire ammeter.

Stopping the hot wire ammeter's pointer when passing an electric current of a certain value.

An electric circuit consists of an AC source (100V – 50Hz) connected in series with resistance 25Ω and inductive coil and capacitor its capacitance 100 μF, if the current intensity and the voltage have the same phase. (π = 22/7). Find:

Inductive reactance (X_L).

The current intensity in the circuit.

Is this circuit at resonance or not? Why?

Second Exam

Question One:

Choose the correct answer:

The AC voltage leads the current by angle 90° when the AC current passes through......

Inductive coil with negligible ohmic resistance

Ohmic resistance

Capacitor

Oscillating circuit

If the inductive reactance of a coil is (440L)Ω sine (L) is the self-induction coefficient of a coil, then the frequency of the current equals.........

44 Hz

70 Hz

400 Hz

140 Hz

The unit of measuring the capacitive reactance is............

V / A

J / C

Henry

V.s / A

In resonance circuit, when the capacitance of the capacitor is increased to double and the inductance of the coil is decreased to its (1/8) value, so the frequency that can be received..........

Doesn't change

Doubled

Decreased to half

Decreased to quarter

AC circuit has an ohmic resistance (R), a coil of inductive reactance (3 R) and a capacitor of capacitive reactance (2R), so the phase angle between the total voltage and the current is.............

45°

30°

90°

60°

First: This opposite circuit consists of some coils with negligible ohmic resistance and AC source. Find:

The total impedance in the circuit.

The total current intensity.

The current intensity in each coil.

Second: An inductive coil with negligible ohmic resistance connected with hot wire ammeter and AC dynamo in series, what will happen to the reading of ammeter at:

Inserting soft iron core inside the coil.

Decreasing the frequency of the source.

Removing 1/4of the coil and connect the rest of the coil with the same source.

A resistance 300Ω is connected in series with capacitor its reactance 265Ω and AC source its frequency 100Hz, if the potential difference across the capacitor = 5 V. (π = 22/7). Calculate:

The capacitor capacitance.

The current intensity in the circuit.

The potential difference across the terminals of the resistance.

Question Two:

Write down the scientific term:

The opposition to the flow of the AC current while passing in a circuit consists of a capacitor due to its capacitance.

………………………………………………………………………………………………………………………………………………………………………….

The angle between the total voltage and AC current.

………………………………………………………………………………………………………………………………………………………………………….

The equivalent of ohmic resistance, capacitive reactance and inductive reactance in RLC circuit.

………………………………………………………………………………………………………………………………………………………………………….

The number of complete cycles which the dynamo's coil rotates around its axis between the poles of the magnet during one second.

………………………………………………………………………………………………………………………………………………………………………….

A current changes its intensity instantaneously and direction periodically.

………………………………………………………………………………………………………………………………………………………………………….

First:

Prove that the term √(L/C) has the same measuring unit of the resistance, where (L) is the self-induction coefficient of the coil and (C) is the capacitor capacitance.

Prove that the term L/R has same unit of the time, where (L) is the self-induction coefficient of the coil and (R) is the ohmic resistance.

Show that (C × R) has the same unit of the time where (C) is the capacitor capacitance and (R) is the ohmic resistance.

Second: Put (√) or (×)

To obtain a high equivalent capacitance from many capacitors, so we connect them in series.

If we connect three capacitors have the same capacitance in parallel, the equivalent capacitance was 4.5 μF, if we connect it in series, the equivalent capacitance becomes 0.5μF.

In the opposite figure if the charge on capacitor (C_1) is 8μC, so the charge on capacitor (C_2) is 16μC.

The equivalent capacitance for group of capacitors connected together in series is more than that of any capacitor of them.

An inductive coil of negligible resistance and ohmic resistance connected with AC source of 50Hz, if the coefficient of self-induction of the coil 0.8H and the resistance is 100Ω and the potential difference across the resistance 12V. (π = 22/7). Calculate:

The current intensity in the circuit.

The potential difference across the coil.

The total potential difference in the circuit.

Question Three:

Mention One application or One use for:

The oscillating circuit.

………………………………………………………………………………………………………………………………………………………………………….

The resonant circuit.

………………………………………………………………………………………………………………………………………………………………………….

The hot wire ammeter.

………………………………………………………………………………………………………………………………………………………………………….

The iridium-platinum wire in the hot wire ammeter.

………………………………………………………………………………………………………………………………………………………………………….

The electric capacitor.

………………………………………………………………………………………………………………………………………………………………………….

First: Prove that the total impedance (Z) for a coil of negligible resistance and ohmic resistance connected in series with it is given from the relation: Z=√(R^2+X_L^2 )

Second: What will happen for?

Increasing the angular velocity of dynamo's coil (with respect to capacitive reactance of capacitor connect with the terminals of the dynamo).

Replacing the AC source with DC source having same emf in the circuit containing inductive coil and ohmic resistance (with respect to the current intensity in the circuit).

Passing an AC current through the moving coil galvanometer.

A circuit consists of ohmic resistance 8 Ω connected in series with an inductive coil of negligible resistance of self-induction coefficient 0.1 H and capacitor of capacitance 12 microfarad and AC source of effective value220V and the number of times of the current reach to zero value in one second is 101 times. Calculate:

The inductive reactance of the coil.

The current intensity passing through a coil.

The phase angle between the total voltage and the current.

What are the modifications that can be done in the circuit to get the maximum effective value of the current in the circuit?

Question Four:

Give reason for:

In the hot wire ammeter, the platinum- iridium wire is mounted on a plate of a metal having the same expansivity as that of the working wire itself.

The capacitors used in the separation of currents of low frequencies from currents of high frequencies.

It is preferred to use AC current than DC current in transmitting from power station to consuming regions.

In platinum-iridium wire is connected in parallel with small resistance "shunt resistance".

First: If you have an AC dynamo with variable angular velocity, ohmic resistance, inductive coil and capacitor. If we connect each of them separately with the dynamo while increasing the angular velocity to the double in each case. Show what will happen to the current intensity in the three components.

Second: Write down the mathematical relation:

The inductive reactance of an inductive of an inductive coil of negligible resistance.

………………………………………………………………………………………………………………………………………………………………………….

The impedance of AC circuit has an inductive coil of negligible resistance and capacitor.

………………………………………………………………………………………………………………………………………………………………………….

The phase angle between the total voltage and the current in RLC circuit.

………………………………………………………………………………………………………………………………………………………………………….

In an AC circuit, it was found that the potential difference between the terminals of capacitor = the potential difference between the terminals of the coil = 20 V. (π = 22/7). Find:

The self-induction coefficient of the coil.

The maximum emf of the source.

The phase angle between the total voltage and the current intensity.

Third Exam

Question One:

Choose the correct answer:

AC circuit of inductive coil has an ohmic resistance and capacitor connected in series, the total impedance is minimum at..........

(Z=X_L)

(X_L=X_C)

〖(X〗_C=R)

〖(X〗_L=R)

Ac circuit consists of inductive coil (negligible ohmic resistance), capacitor and non-inductive ohmic resistance, the phase angle between total voltage and current is equal zero at.........

(Z=X_L)

(Z=X_C)

(V_L=V_C)

(V_L=V_R)

The scale of the hot wire ammeter is non-uniform because the............

Current intensity is inversely proportional to with total resistance in ammeter circuit

Thermal energy produced in ammeter's wire directly proportional to coil resistance

Current intensity inversely proportional to the resistance of platinum-iridium wire

Produced thermal energy in the ammeter's wire is directly proportional to the square of the current intensity passing

The inductive reactance of the coil is given from the relation..........

X_L=1/2πf

X_L=2πfC

X_L=2πfL

X_c=1/2πfC

The equivalent capacitive reactance for two capacitors connected in series.............

X_CT=1/X_C1 +X_C2

X_CT=(X_C1×X_C2)/(X_C1+X_C2 )

X_CT=X_C1+X_C2

1/X_CT =1/X_C1 +1/X_C2

First: Mention only Two factors affecting on:

The impedance of the AC circuit has a capacitor and inductive coil connected in series.

………………………………………………………………………………………………………………………………………………………………………….

The phase angle between the total voltage and the current in AC circuit consists of inductive coil has an ohmic resistance.

………………………………………………………………………………………………………………………………………………………………………….

The value of the current in AC circuit has a capacitor and ohmic resistance connected in series.

………………………………………………………………………………………………………………………………………………………………………….

Second: Compare between each:

AC current and DC current (with respect to the nature of each).

Hot wire ammeter and moving coil ammeter (with respect to scientific idea based on).

The coil and the capacitor (with respect to the kind of stord energy in each of them when connected with electric source).

The points (A) and (B) in the opposite figure are connected with AC source of emf 200V and frequency 50Hz. Find:

The current intensity passes in the circuit.

The potential difference between (A & C).

The potential difference between (C & B).

Question Two:

Give reason for:

Cutting a part from the solenoid and connecting the remaining part with the same source, then its inductive reactance will decrease.

There is no energy consumed in the capacitor although it has a capacitive reactance.

The hot wire ammeter is connected in series in the electric circuit.

Practically, there is no inductive coil with non-ohmic resistance.

The DC current cannot passes in the capacitor circuit while the AC current can pass through it.

First: Write down the mathematical formula:

The capacitor's capacitance in terms of its properties.

………………………………………………………………………………………………………………………………………………………………………….

The total inductive reactance for two inductive coils connected in parallel.

………………………………………………………………………………………………………………………………………………………………………….

The total current intensity for a circuit consists of a coil has an ohmic resistance and connected with AC source.

………………………………………………………………………………………………………………………………………………………………………….

Second: What is meant by?

The total impedance in RC circuit = 200Ω.

………………………………………………………………………………………………………………………………………………………………………….

The AC circuit has an inductive coil and capacitor in case of resonance.

………………………………………………………………………………………………………………………………………………………………………….

The periodic time of AC current = 0.02 second.

………………………………………………………………………………………………………………………………………………………………………….

AC circuit consists of a source 200 V, a coil its ohmic resistance 36Ω and its inductive reactance 90Ω, a capacitor its capacitive reactance 30Ω and an ohmic resistance 44Ω connected in series. Calculate potential difference across each component in the circuit.

Question Three:

What will happen when?

Connecting a capacitor with DC source.

………………………………………………………………………………………………………………………………………………………………………….

Passing AC current in the moving coil ammeter.

………………………………………………………………………………………………………………………………………………………………………….

Mounting the wire made of platinum-iridium on a plate made of a metal having different expansivity as that of the working wire itself.

Passing AC current in circuit contains an inductive an inductive coil and ohmic resistance in series.(with respect to phase angle)

Inserting a soft iron core inside inductive coil connected in series with ohmic resistance in AC circuit. (with respect to value of current)

………………………………………………………………………………………………………………………………………………………………………….

First: An inductive coil, the potential difference between its terminals is 43.8V when the current changes with a rate 125A/sec. Calculate the inductive reactance of the coil. (Knowing that the frequency of the source is 60 Hz).

A lamp (120 V – 60 Watt) is connected with AC source (240 V – 50 Hz) and capacitor in series. What is the capacitance of the capacitor which allow to pass maximum current through the lamp?

Question Four:

What is the necessary condition (reason) for?

Capacitor has constant capacitance, its capacitive reactance tends to zero in AC circuit.

In RLC circuit, the phase angle between the total voltage and the current equals zero.

The total voltage leads the current by angle 90° in AC circuit.

………………………………………………………………………………………………………………………………………………………………………….

A resonance circuit in tuning radio receiver receives a wave with certain frequency.

Consuming energy in the oscillating circuit.

First: Three capacitors of capacitance 1, 2, and 3 μF are connected in series with AC source 22V. Find the potential difference between the two plates of each capacitor.

Second: What are the results of?

Increasing the capacitor capacitance in RC circuit at constant potential difference and frequency (with respect to the current).

………………………………………………………………………………………………………………………………………………………………………….

Double wounding the wires of the coil (with respect to its inductive reactance).

………………………………………………………………………………………………………………………………………………………………………….

Decreasing the distance between the solenoid coil turns to half (with respect to its inductive reactance).

………………………………………………………………………………………………………………………………………………………………………….

The following table shows the relation between the inductive reactance of a coil (X_L) and the frequency (f) of the current passing through it.

X_L (Ω) 50 100 150 A 300 400

f (Hz) 10 20 30 50 B 80

Draw the relation between the inductive reactance (X_L) of the coil on vertical axis and the frequency (f) on the horizontal axis. From the graph find:

The value of (A) & (B).

The self-induction coefficient of a coil.

The capacitor's capacitance which must be connected in the circuit to reach resonant condition when the frequency is 30 Hz.

FIFTH: EXAMS ON Chapter (5)

WAVE PARTICLE DUALITY

Essay Questions:

Show why the wave theory failed to explain the photoelectric effect, and how Einstein managed to interpret the experimental results of this phenomenon.

Show how to verify the particle nature of light from the black body radiation.

Explain the Compton effect and show how it proves the particle nature of light?

Problems:

Calculate the energy of a photon whose wavelength is 770 nm and find its mass and linear momentum? (2.58×〖10〗^(-19) J,0.29×〖10〗^(-35) kg,0.8×〖10〗^(-27) kgm/s)

Calculate the mass of an X-ray photon and a γ ray photon if the wavelength of X-ray is 100nm, and that of γ-ray is 0.05 nm (m_X=2.2×〖10〗^(-35) kg,m_γ=4.4×〖10〗^(-32) kg )

Calculate the wavelength of a ball whose mass is 140 kg which moves at velocity 40 m/s Also, calculate the wavelength of an electron if it has the same velocity.

(λ=1.18×〖10〗^(-37) m,λ_e=1.8×〖10〗^(-5) m)

A radio station emits a wave whose frequency is 92.4 MHz. Calculate the energy of each photon emitted from this station. Also calculate the rate of photons ϕ_L if the power of the station is 100 kW.

(E=612.15×〖10〗^(-28) J,ϕ_L=16.3×〖10〗^29 Photon/s)

An electron is under a potential difference 20 kV. Calculate its velocity upon collision with the anode from the law of conservation of energy. The electron charge is 16×〖10〗^(-19) C, its mass is 9.1×〖10〗^(-31) kg. Then calculate 𝛌 and P_L.

(V=0.838×〖10〗^8 m/s,λ=0.868×〖10〗^(-11) m,〖 P〗_L=7.625×〖10〗^(-23) kgm/s)

If the least distance delected with an electron microscope is 1nm, calculate the velocity of the electrons and the potential of the anode.

(Velocity=0.725×〖10〗^6 m/s,V=1.5 Volt)

Calculate the force by which an e-beam whose power is 100 kW affects an object whose mass is 10 kg, what happens if the object is an electron and why?

(0.67×〖10〗^(-3) N)

First Exam

Question One:

What is meant by?

Wien's law.

………………………………………………………………………………………………………………………………………………………………………….

Black body.

………………………………………………………………………………………………………………………………………………………………………….

Photoelectric effect.

………………………………………………………………………………………………………………………………………………………………………….

Work function energy.

………………………………………………………………………………………………………………………………………………………………………….

Planck's distribution.

………………………………………………………………………………………………………………………………………………………………………….

First: Compare between photons and electrons with respect to (Definition – momentum – mass at rest).

Second: Give reasons for:

The wavelength associated with the electron decreases with the increase of its speed.

Electron microscope has larger resolving power than that of optical microscope.

Compton Effect describes the particle nature of photons.

An incident monochromatic light of wavelength 5000 A° on metal surface emits electrons with maximum velocity 2.57×〖10〗^5 m/s. If another monochromatic light is incident of wavelength 6000 A° on this metal surface. Do electrons release from the metal? Why? (m_e=9.1×〖10〗^(-31) Kg,h=6.6×〖10〗^(-34) J.s,c=3×〖10〗^8 m/s)

Question Two:

Mention the scientific idea (basic) for:

Cathode ray tubes.

………………………………………………………………………………………………………………………………………………………………………….

Photoelectric cell.

………………………………………………………………………………………………………………………………………………………………………….

Remote sensing.

………………………………………………………………………………………………………………………………………………………………………….

Electron Microscope.

………………………………………………………………………………………………………………………………………………………………………….

First: What is meant by?

Critical wavelength for metal (λ_c) = 5000 A°.

Critical frequency (υ_c) for metal surface =4.8×〖10〗^14 Hz .

Second: State One of the factors that will depend upon:

The work function energy of a metal surface.

………………………………………………………………………………………………………………………………………………………………………….

Photoelectron current intensity.

………………………………………………………………………………………………………………………………………………………………………….

Wavelength with a maximum intensity of radiation from glowing body.

………………………………………………………………………………………………………………………………………………………………………….

Question Three:

Mention One application:

Cathode ray tube.

………………………………………………………………………………………………………………………………………………………………………….

Photoelectric cell.

………………………………………………………………………………………………………………………………………………………………………….

Infrared radiation.

………………………………………………………………………………………………………………………………………………………………………….

Microwaves.

………………………………………………………………………………………………………………………………………………………………………….

First: Explain how could the scientist Max Planck explain the black body radiation phenomenon.

Second: The opposite figure shows the relation between the intensity of radiation emitted from hot bodies and wavelength. If the surface temperature of the sun is 6000K, use the data on the figure to calculate the earth's surface average temperature.

The graph shows the relationship between the maximum kinetic energy of electrons emitted from three metals and the frequency of light falling on them. Depending on the graph:

Calculate the work function for metal (b).

If a light with certain frequency falls to liberate electrons from the three metals, which of these free electrons have more K.E?

If a monochromatic light of frequency (7×〖10〗^14 Hz ) falls on each metal, what is the value of the maximum kinetic energy for the electrons in case of releasing from the metal?

What is the minimum suitable frequency required to liberate electrons from any of these metals.

Question Four:

What are the results of?

Heating a metallic surface to very high temperature. (with respect to the free electrons inside metallic surface).

Increasing frequency of radiation emitted from glowing body. (With respect to intensity)

Falling light on metal surface with energy more than the work function of that surface.

Falling a photon (γ-rays) on a free electron.

Increasing the momentum of a particle (With respect to wavelength accompanied).

First: How can Einstein explain the photoelectric effect?

Second: Choose the correct answer:

Laser source of power (300mW) at wavelength (6630A°), so the number of emitted photons from this source in each minute is..........electrons.

6×〖10〗^19

6×〖10〗^18

6×〖10〗^17

6×〖10〗^16

6×〖10〗^14

If the mass of proton at rest is (m_o), so its momentum when it moves with velocity equal half the velocity of light in space (c) can be calculated from the relation............

(3m_o c)/4

(m_o c)/2

(m_o c)/√3

(2m_o c)/√3

This graph shows the maximum kinetic energy for the emitted electrons from potassium metal at number of frequencies.

Which of the following graphs shows the correct comparison when replacing the potassium with silver of work function (4.73eV)

This table shows the relation between the wavelengths (λ) of the De-Broglie wave accompanied to moving particle with velocity (v):

λ×〖10〗^(-20) (m) 2 4 6 8 10

v×〖10〗^(-3) (m/sec) 100 50 X 25 20

Draw the relation between the wavelength (λ) on y-axis and the reciprocal of the velocity on x-axis and from the graph, Find:

The value of (X).

The mass of the particle. (h=6.6×〖10〗^(-34) J.s)

Second Exam

Question One:

What is meant by?

Photon.

………………………………………………………………………………………………………………………………………………………………………….

Compton Effect.

Surface potential barrier.

Remote sensing.

Dual nature for particle.

First: Compare between each:

Radiation from the sun (glowing body) and the radiation from earth (non-glowing body) (with respect to spectrum region at which maximum radiation intensity occurs).

Electron and optical microscope (with respect to kind of radiation used and type of lenses).

Second: Give reasons for:

The radiation emitted from human body cannot be seen.

It is possible that the photons fall on a metal and do not case the emission of electrons from it.

X-ray photon falls on a free electron, the electron speed increases and change its direction.

Light with wavelength (λ)falls on a metal surface and emits electrons with maximum kinetic energy (1 eV), while when another light with wavelength (λ/2) incident on the same metal surface, electrons emitted with maximum kinetic energy (4 eV). Calculate the work function of the metal surface.

Question Two:

What is the necessary condition for?

Seeing the dimensions of a minute body using microscope.

Releasing of electrons from metal surface when light falls on it.

First: Compare between the wavelength accompanied to each of electron and proton according to De-Broglie equation, if they move with same velocity.

Second: Mention One application:

Wien's law.

………………………………………………………………………………………………………………………………………………………………………….

Dual nature for electron.

………………………………………………………………………………………………………………………………………………………………………….

The heat radiated from the human body.

………………………………………………………………………………………………………………………………………………………………………….

Light beam of wavelength 8×〖10〗^(-7) m and power 200W falls on certain surface. Calculate:

The momentum of the photon from this radiation.

The beam's force acting on the surface on its reflection.

Question Three:

State One use for:

Cathode ray tube.

………………………………………………………………………………………………………………………………………………….

………………………………………………………………………………………………………………………………………………………………………….

Photoelectric cell:

…………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………….………………..……………………………………

Infrared rays.

………………………………………………………………………………………………………………………………………………….

Microwave

……………………….………………………………………………………………………………………………………………………..

………………………………………………………………………………………………………………………………………………….

In photoelectric emission experiment, a metal surface in an evacuated tube was illuminated with monochromatic light of frequency greater than the critical one for such metal. If the experiment is repeated with light of the same wavelength, but of twice the intensity, what will be the effect of that on:

The photon energy.

The maximum kinetic energy of the photoelectron.

The work function of the metal.

The photocurrent.

………………………………………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

The graph shows the relation between maximum kinetic energy for emitted electrons from metal surface (A) and frequency of the incident on it. From the graph:

What is the critical frequency for the metal?

Calculate wavelength of light which emit electrons with maximum kinetic energy (20×〖10〗^(-20) J).

If the metal (A) is replaced by another metal (B) of double the critical frequency for metal (A). Draw on the same graph the relation between maximum kinetic energy for emitted electrons from metal surface (B) and frequency of the incident light falling on it. Show what happens to the resulted line slope with explaining the answer.

………………………………………………………………………………………………………………………………………………….

………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………….………………..

………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………….………………..

Question Four:

The opposite diagram shows Cathode Ray Tube.

What do cathode rays consists of?

Which part A, B, C or D is the source of the cathode rays?

Which part A, B, C or D is coated with fluorescent material? Why?

What is the effect when connecting potential difference between the two terminals of part (C) on cathode ray tube?

………………………………………………………………………………………………………………………………………………….

………………………………………………………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………….

First: Deduce the relation between wavelength of the photon and linear momentum.

………………………………………………………………………………………………………………………………………………….

Second: Choose the correct answer:

Accelerating a stationary electron under the effect of 2500V. What is the final velocity approximately?

3×〖10〗^6 m/s

1.5×〖10〗^8 m/s

2.5×〖10〗^6 m/s

2.5×〖10〗^8 m/s

3×〖10〗^7 m/s

If momentum of a body increased by 25%, then its kinetic energy nearly increased by.........

65%

56%

38%

25%

If kinetic energy of a body increased 16 times, then the percentage change for the wavelength of De-Broglie is..........

75%

60%

50%

30%

25%

Monochromatic light incident of photon energy (5.8eV) on a metal surface which emits photoelectrons with maximum kinetic energy (1.2eV), using the table to answer:.

Metal Sodium Zinc Potassium Tungsten

E_W (eV) 2.36 2.65 2.28 4.6

Calculate the frequency of light's photons incident on the metal surface.

Determine the name of the metal which photoelectrons emitted from its surface. Explain your answer.

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