Physics Electromagnetism MCQs Chapter 3 Class 12

Created on February 07, 2022 By Ali Durrani

Physics Ch 14 Class 12 ELECTROMAGNETISM

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1 / 74

A conductor of length L is moved across a magnetic field. Due to this activity, a potential difference appears across the ends of the conductor. This type of potential difference is termed as:

NTS 2018
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Self Induction

B) Mutual Induction

C) Motional EMF

D) Electrostatic potential

2 / 74

If the length of a current carrying solenoid is doubled keeping the number of turns same and the current is increased to 9 times, the value of magnetic field compared to the original magnetic field B will be:

2/9 B

9/2 B

18B

B/18

3 / 74

Magnetic effect of electric current was first discovered by

Faraday

Oersted

Henry

None of these

4 / 74

If a certain region’s magnetic field is directed vertically up and a proton enters this field from the left side, it will go _________.

NUMS 2019 Reconduct
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Up

B) Down

C) Right

D) Towards us

5 / 74

Transformer is a device which steps up or steps down the input:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Current

B) Voltage

C) Energy

D) Power

6 / 74

Weber x ampere per meter is equal to:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Joule

B) Watt

C) Newton

D) Henry

7 / 74

A conductor carrying a current ‘I’ has length ‘L’. When it is placed in a magnetic field, ‘B’ at 90 degrees , it experiences a force:

NTS 2016 DUHS & JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) BLI

B) B2LI

C) BLI2

D) Zero

8 / 74

Transformer works on the principle of:

NTS 2016 SMBBMC
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Self induction

B) Mutual magnetic induction

C) Electrostatics

D) Mutual charging

9 / 74

F = I L B, What Is relation between I and L

Direct

Inverse

Inverse of square

None of the above

10 / 74

If a constant current is flowing through a coil, then the flux through that coil will become constant. In such types of arrangements, the electromotive force (emf) induced in the coil will be:

NTS 2018
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Self-Inductance

B) Zero

C) Mutual-Inductance

D) Back EMF

11 / 74

In a circuit, there is a current of 5 amp which is changed such that the current falls to zero in 0.1 sec. If an average e.m.f. of 200 volts is induced, the self-inductance of the circuit will be:

NTS 2012
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 4 Henrys

B) 5 Henrys

C) 6 Henrys

D) 7 Henrys

12 / 74

There is a current of 25 A in a long straight wire. What is the flux density at a point 3 cm from the wire?

NTS 2016 SMBBMC
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 1.67 x 10-4 T

B) 3.67 x 10-4 T

C) 5.67 x 10-4 T

D) 7.67 x 10-4 T

13 / 74

In a certain circuit, a transistor has a collector current of 10mA and a base current of 40μA. What is the current gain of the transistor?

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 150

B) 200

C) 250

D) 300

14 / 74

By changing the current through the same coil, an emf is induced in it, the process is known as:

NTS 2015 SMBBMC
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Rectification

B) Mutual induction

C) self induction

D) simple induction

15 / 74

In transmission from grid station, power losses are minimized by:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Increasing current

B) Decreasing current

C) Increasing resistance

D) Increasing voltage

16 / 74

Magnetic force on a moving charge depends upon:

NTS 2016 SMBBMC
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Magnetic field and charge only

B) Magnetic field and speed of the charge only

C) Charge and speed of the charge only

D) Magnetic field, charge and speed of the charge

17 / 74

When a transformer is connected to 120-volt ac, it supplies 3000 V to a device. The current through the secondary winding then is o.06 A and the current through the primary is 2 A. The number of turns in the primary winding is 400. The number of turns in the secondary winding is:

NTS 2016 DUHS & JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

B) 30

C) 1000

D) 2000

E) 10000

18 / 74

Ammeter Is a galvanometer with:

High resistance in series

Low resistance in series

High resistance in parallel

Low resistance in parallel

19 / 74

Unit of Magnetic Flux is

Weber

Tesla

Volt

Weber/m

20 / 74

If two inductors each of Inductance L are Introduced in a circuit in parallel, the equivalent Inductance will be:

2L

L

3L/2

L/2

21 / 74

A circuit in which there is a current of 10 amperes is changed so that the current falls to zero in 0.5 seconds. If an average e.m.f. of 400 volts is induced, what is the self-inductance of the circuit?

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 10 henrys

B) 20 henrys

C) 30 henrys

D) 40 henrys

22 / 74

Two parallel straight conductors, in which current is flowing in the same direction, attract each other. The cause of it is:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) magnetic force between the two

B) electric force between the two

C) potential difference between the two

D) mutual induction between the two

23 / 74

In a coil, when current changes from 10 A to 4 A in 1 s. An induced emf of 1.2 V is induced across the coil. The self – inductance of the coil is:

NUMS 2019 Cancelled
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 2 H

B) 0.2 H

C) 0.002 H

D) 5 H

24 / 74

A force which is experienced in a magnetic field depends on:

NTS 2011
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) magnitude of charge

B) speed of the moving charge V

C) magnitude field of induction B

D) all of these

25 / 74

An electron is moving along the axis of a solenoid carrying a current. Which of the following is a correct statement about the electromagnetic force acting on the electron?

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) The force acts perpendicular to its motion

B) The force acts anti-parallel to its motion

C) The force acts in the direction of motion

D) No force acts

26 / 74

A torold is? l• A circular ring shape of a coil. II- A solenoid bent In shape of a circle. a) I only b) II only

I only

II only

Both I and II

None of these

27 / 74

Magnetic flux is maximum when angle between magnetic field and vector area is:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 0

B) 90

C) 180

D) 45

28 / 74

The SI unit of magnetic flux is Weber which is equivalent to:

NUMS 2019 Reconduct
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) NA / m

B) NmA

C) Nm-1A-1

D) Nm / A

29 / 74

If the direction of current in two parallel wires is In opposite direction, then the wires will:

Attract

Repel

Both a and b

None of these

30 / 74

A 20.0 cm wire carrying a current of 10.0 A is placed in a uniform magnetic field of 0.30 T. If the wire makes an angle of 40° with the direction of the magnetic field, find the magnitude of the force acting on the wire? ( sin 40° = 0.642)

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 2.71 N

B) 0.39 N

C) 6.61 N

D) 7.61 N

31 / 74

What is true regarding magnetic force and magnetic intensity?

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) If an electron's movement is parallel to the magnetic field. it will rotate

B) If electron's movement is parallel to magnetic field, it Will rotate anticlockwise

C) If an electron enters perpendicular to the field force it would be parallel to the plane.

D) If an electron enters perpendicular to the field force will be maximum. nn

32 / 74

An electron enters in a magnetic field at an angle less than 90 degrees with magnetic field. Which of the following path is followed by an electron?

NUMS 2014
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Straight

B) Circular

C) Curve

D) Helical

33 / 74

What is the dimension of magnetic field

LA^-3T^-1

ML^-2T^-2

ML^-3TA^-1

ML^-2A^-1

34 / 74

A circuit in which there is a current of 5 amp is changed so that the current falls to zero in 0.1s. If an average e.m.f of 200 volts is induced, what is the self-inductance of the circuit?

NTS 2014
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 4 henrys

B) 8 henrys

C) 12 henrys

D) 16 henrys

35 / 74

How fast an H+ ion should move in magnetic field 2.5×10-3 T such that magnetic force equal its weight?

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 6 x 10-5 m/s

B) 4.5 x 10-5 m/s

C) 3.3 x 10-6 m/s

D) 4 x 10-5 m/s

36 / 74

When the ohmmeter measures the infinite resistance, its pointer lies at

Centre of the scale

Left end of the scale

Right end of the scale

None of these

37 / 74

Two point charges of +5 C and -12 C attract each other with a force of 1.48 N. charge of -5 C is added to each of these charges. Now the force will be:

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 1.48 N (attractive)

B) 1.48 N (repulsive)

C) 2.96 (repulsive)

D) Zero

38 / 74

A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1kV, its kinetic energy will be:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 1840 keV

B) 1/1840 keV

C) 1keV

D) 920 keV

39 / 74

Ammeter lies in

Series

Parallel

Either a or b

None of these

40 / 74

EEG is related to:

Heart

Brain

Both a and b

None of the above

41 / 74

A coil of 600 turns is threaded by a flux of 8×10-5 webers if this flux is reduced to 3×10-5 webers in 0.015 seconds. The average induced e.m.f. is:

NTS 2011
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) -2.0 volts

B) -3.0 volts

C) +2.0 volts

D) +2.5 volts

42 / 74

If length of solenoid gets doubled while keeping N (number of turns) constant, the resultant magnetic field will be?

B/2

B/4

2B

B/3

43 / 74

In CRO, electrons are emitted from:

Filament

Cathode

Anode

Electron Gun

44 / 74

What is the device which is used to measure magnetic field

Magnetometer

Voltmeter

Wilson-cloud chamber

None of the above

45 / 74

A particle of charge -0.04C is projected with speed 2 x 104 m/s into a uniform magnetic field ‘B’ of strength 0.5 T. If the particle’s velocity as it enters the field is perpendicular to ‘B’, what is the magnitude of the magnetic force on this particle:

NTS 2010
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

B) 8 N

C) 40 N

D) 80 N

E) 400 N

46 / 74

Unit of magnetic flux density is

wb/mz

N/Am

Tesla

All of these

47 / 74

Due to the magnetic force, a positively charged particle executes uniform circular motion within a uniform magnetic field ‘B’. If the charge is ‘q’ and radius of its path is r, which of the expressions gives the magnitude of the particle’s linear momentum:

NTS 2010
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) qBr

B) qB/r

C) q/(Br)

D) B

48 / 74

If a stationary bar magnet is placed near a coil so that maximum lines of force passes through the coil, the galvanometer shows:

PMC 2020
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Maximum current

B) Minimum current

C) No current

D) Intermediate value of current

49 / 74

A circuit in which there is a current of 5 amp is changed so that the current falls to zero in 0.1 s. If an average e.m.f of 200 volts is induced, what is the self inductance of the circuit?

NTS 2016 SMBBMC
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 1 Henrys

B) 2 Henrys

C) 3 Henrys

D) 4 Henrys

50 / 74

ECG records

Voltage from the heart

Stress

Heartbeat

None of these

51 / 74

The combination of ammeter, voltmeter, and ohmmeter into a compact single meter with one common galvanometer is called:

NTS 2015 SMBBMC
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Post office box

B) AVO meter

C) Meter bridge

D) Microscope

52 / 74

The brightness spot on the screen in the CRO is controlled by:

Anode

Cathode

Grid

Filament

53 / 74

If electron passes through axis of solenoid the movement will be:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Towards the outward

B) Towards the inward

C) Parallel to its motion

D) No force acts on it

54 / 74

If a wire having current 10A has a 3T magnetic field, what will be the magnetic field at a point from the wire at double the distance?

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Reduces by factor 2

B) Becomes double

C) Reduces by factor 4

D) Becomes triple

55 / 74

The current measuring part of the Avometer consists of a number of low resistors connected …

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) At an angle of 180 degrees with the galvanometer

B) Parallel with galvanometer

C) At an angle of 45 degrees With the galvanometer

D) Perpendicular with the galvanometer

56 / 74

A current carrying conductor is lying perpendicular to magnetic field and experiencing some force. If the conductor rotates by 60 degrees counter clock wise, the force on it will

Increase

Decrease

Will be same

None of these

57 / 74

What are dimensions of Magnetic Flux

a

b

c

d

58 / 74

A bar magnet has a magnetic moment 200 Am2. The magnet is suspended in a magnetic field of 0.30 NA-1m-1. The torque required to rotate the magnet from its equilibrium position at an angle of 30˚ will be:

NUMS 2014
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 30Nm

B) 3073 Nm

C) 60Nm

D) 604Nm

59 / 74

the value of permeability

a

b

c

d

60 / 74

_______ is a device which makes use of mutual induction for stepping up or down an alternating e.m.f.

NTS 2012
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Sonometer

B) Transformer

C) Ammeter

D) Voltmeter

61 / 74

1 testa is equal to?

10^4 Gauss

Wb/m

Both a and b

None of these

62 / 74

A magnetic needle is placed in a uniform magnetic field and is aligned with the field. The needle is now rotated by an angle of 60 degrees and work done is W. The torque on the magnetic needle at this position is

NUMS 2014
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 2√3 W

B) √3 W

C) √(3/2) W

D) √(3/4) W

63 / 74

An A.C emf of E = 100 sin (100 π t) volt is concerned with a choke of negligible resistance. In order to produce current of amplitude 1 A, the inductance of the choke should be:

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 200 H

B) 2π H

C) 1 /πH

D) 2 /πH

64 / 74

Identify the instrument/s which is/are used for the measurement of resistance:

I. Wheatstone Bridge

II. Meter Bridge

III. Post office Box

IV. Ohmmeter

NTS 2015 DUHS and JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

B) I and II only

C) II and III only

D) III and IV only

E) I, II, III, and IV

65 / 74

Which of the following is incorrect?

F ∝ l

F ∝ sine

F ∝ L

F ∝ 1/B

66 / 74

If the current in the wire is directed into the page, and the wire is held perpendicular to the page, then the direction of magnetic circles will be:

Clockwise

Anticlockwise

Both a and b

None of these

67 / 74

Four particles independently move at the same speed in a direction perpendicular to the same magnetic field. Which particle is deflected the most?

NTS 2017
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) a copper ion

B) a helium nucleus

C) an electron

D) a proton

68 / 74

The direction of the magnetic line of force depends upon:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Nature of the material of the conducting wire

B) Area of the conducting wire

C) Amount of the current

D) Direction of the current

69 / 74

A 3-cm length of wire is moved at right angles across a uniform magnetic field with a speed of 2.0 m/s . If the flux density is 5.0 teslas, what is the magnitude of the induced e.m.f?

NTS 2016 DUHS & JSMU
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 0.03 V

B) 0.3 V

C) 0.6 V

D) 10 V

70 / 74

Moving charge produce field

Electric

Magnetic

Both a and b

None of these

71 / 74

If current passing through a solenoid is increased, which of the following must increase:

Length of solenoid

Number of turns

Magnetic field

All of these

72 / 74

A 3-cm length of wire is moved at right angles across a uniform magnetic field with a speed of 2.0 m/s . If the flux density is 5.0 teslas, what is the magnitude of the induced e.m.f?

NUMS 2015
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 0.03 V

B) 0.3 V

C) 0.6 V

D) 10 V

73 / 74

When a charged particle is projected perpendicular to a magnetic field:

NUMS 2016
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) Its path is circular in a plane perpendicular to the plane of magnetic field

B) The speed and kinetic energy of the particle remains constant

C) The velocity and momentum of the particle changes only in direction

D) The time period of revolution, angular and frequency of revolution is independent of velocity of the particle and radius of circular path

74 / 74

What is the flux density at a point 3 cm from the long straight wire, when there is a current of 25 A in a wire: (u0= 4? x10-7)

NTS 2010
Physics
Magnetism and Electromagnetic Induction
Elimination Tool:

A) 0.23×10-1 T

B) 1.67x 10-4 T

C) 2.99×10-6 T

D) 3.63×10-8 T

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Physics Electromagnetism MCQs Chapter 3 Class 12

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