# 12th Class Physics Chapter 14 MCQs with Answers

Welcome to the 12th Class Physics Chapter 14 MCQs Online Test. We are presenting you with top MCQ questions from the 12th Class Physics Chapter  ELECTROMAGNETISM.

Contents

## 12th Class Physics Chapter 14 MCQs with Answers

Electromagnetism is a captivating branch of physics that explores the intricate relationship between electricity and magnetism. It unravels the profound connection between electric currents and magnetic fields, paving the way for a deeper understanding of various phenomena and the development of numerous technological applications.

The study of electromagnetism encompasses a wide range of topics, including the behavior of electric charges in motion, magnetic fields, electromagnetic induction, and electromagnetic waves.

One of the fundamental concepts in electromagnetism is Ampere’s law, which establishes the relationship between electric currents and the magnetic fields they generate. Students will explore the principles of magnetic fields, magnetic flux, and magnetic field lines, gaining insights into the behavior of magnetic materials and the forces acting on charged particles in magnetic fields.

Electromagnetic induction, another key aspect of electromagnetism, introduces the concept of generating electric currents through changing magnetic fields. Students will delve into Faraday’s law of electromagnetic induction, Lenz’s law, and the concept of self-induction. This understanding forms the basis for the operation of electric generators, transformers, and other devices essential to modern power systems.

Moreover, electromagnetism encompasses the study of electromagnetic waves, which include visible light, radio waves, microwaves, and X-rays. Students will explore the properties of electromagnetic waves, including their propagation, polarization, and the electromagnetic spectrum. This knowledge is vital for understanding various communication technologies, optics, and the behavior of light.

The study of electromagnetism often involves the use of mathematical equations, such as Maxwell’s equations, which describe the fundamental principles of electromagnetic fields. Students will encounter vector calculus and learn to apply these equations to analyze complex electromagnetic phenomena.

Practical applications of electromagnetism are widespread and diverse. They include electric motors, transformers, wireless communication systems, MRI machines, and many more. Understanding electromagnetism equips students with the knowledge to comprehend and contribute to advancements in technology, engineering, and various scientific fields.

By studying electromagnetism, students develop a profound understanding of the deep interplay between electricity and magnetism, enabling them to comprehend the fundamental forces governing the natural world and apply this knowledge to real-world situations and technological innovations.

### What is  ELECTROMAGNETISM?

Electromagnetism is the physical interaction among electric charges, magnetic moments, and the electromagnetic field. The electromagnetic field can be static, slowly changing, or form waves. Electromagnetic waves are generally known as light and obey the laws of optics.

Chapter 14 ELECTROMAGNETISM

1. The name of the scientist who noted that a compass needle was deflected when placed near the current carrying conductor choose which one is correct:

(a) Henry

(b) Faraday

(c) Coloumb

(d) Oersted

Answer
(d) Oersted

2. The sources of magnetic field are choose which one is correct:

(a) Charges in the motion

(b) Charges at rest

(c) Both (a) and (b)

(d) None of above

Answer
(a) Charges in the motion

3. A current carrying conductor placed in a magnetic field parallel to it. The force experienced by the conductor is choose which one is correct:

(a) F = O

(b) F = BIL

(c) F = BIL sin0

(d) F = BIL cos0

Answer
(a) F = O

4. Who discovered a relation between magnetic and electric field choose which one is correct:

(a) Lenz

(b) Faraday

(c) Oersted

(d) None of above

Answer
(c) Oersted

5. A changing magnetic field produces choose which one is correct:

(a) Electric current

(b) Electric field

(c) Magnetic field

(d) None of above

Answer
(a) Electric current

6. The direction of magnetic lines of force are depend upon choose which one is correct:

(a) Direction of current

(b) Quantity of current

(c) Both (a) and (b)

(d) None of the above

Answer
(c) Both (a) and (b)

7. The force acting on one metre length of the conductor placed at right angle to the magnetic field is called choose which one is correct:

(a) Magnetic field

(b) Magnetic induction

(c) Force

(d) None of the above

Answer
(b) Magnetic induction

8. The dot product of magnetic field B and vector area A is choose which one is correct:

(a) Magnetic flux

(b) Magnetic induction

(c) Faraday’s law

(d) Electric flux

Answer
(a) Magnetic flux

9. which instrument among the following can measure potential without drawing any current is called choose which one is correct:

(a) Voltmeter

(b) Potentiometer

(c) CRO

(d) Ammeter

Answer
(b) Potentiometer

10. Tesla is the unit for measuring choose which one is correct:

(a) Magnetic intensity

(b) Magnetic induction

(c) Magnetic force

(d) None of the above

Answer
(b) Magnetic induction

11. Weber is the unit of choose which one is correct:

(a) Magnetic flux

(b) Permeability

(c) Magnetic force

(d) None of above

Answer
(a) Magnetic flux

12. Weber has the dimensions of choose which one is correct:

(a) volt/sec

(b) volt2/sec

(c) volt/sec2

(d) sec/volt

Answer
(a) volt/sec

13. The cathode ray oscilloscope is useful for choose which one is correct:

(a) A volt meter

(b) Wave shape of rapidly charging lubricants

(c) Measuring time interval between electrical plates

(d) All of the above

Answer
(b) Wave shape of rapidly charging lubricants

14. What is emitted by the hot metal filament in a cathode ray oscilloscope choose which one is correct:

(a) Electron

(b) X-plates

(c) Protons

(d) Y-plates

Answer
(a) Electron

15. When the angle between the vector area and the magnetic field is 00 then magnetic flux is choose which one is correct:

(a) Half

(b) Minimum

(c) Maximum

(d) Double

Answer
(c) Maximum

16. When some compass needles are placed on a cardboard along a circle with the center at the wire, they will choose which one is correct:

(a) Set themselves tangential to the circle

(b) Points in the direction of N-S

(c) Points in the direction of E.W

(d) None of these

Answer
(a) Set themselves tangential to the circle

17. In the region surrounding a current carrying wire choose which one is correct:

(a) A magnetic field is setup

(b) The lines of force are elliptical

(c) Both (a) and (b)

(d) None of these

Answer
(c) Both (a) and (b)

18. Magnetic force acting on unit positive charge moving perpendicular to the magnetic field with a unit velocity is known as choose which one is correct:

(a) Magnetic induction

(b) Magnetic flux

(c) Magnetic field density

(d) None of these

Answer
(a) Magnetic induction

19. How are the electrons produced in a cathode ray oscilloscope choose which one is correct:

(a) By heating a metal filament

(b) By ionization of the air

(c) By applying an electric field

(d) None of these

Answer
(a) By heating a metal filament

20. The function of grid in cathode ray oscilloscope is choose which one is correct:

(a) To control the number of electrons accelerated by anode

(b) To control the brightness of spot formed on the screen

(c) Both (a) and (b)

(d) None of these

Answer
(c) Both (a) and (b)

21. Magnetic field is a choose which one is correct:

(a) Scalar quantity

(b) Vector quality

(c) Both (a) and (b)

(d) None of these

Answer
(b) Vector quality

22. The direction of magnetic lines of force around a current carrying conductor is given by choose which one is correct:

(a) Coulombs law

(b) Ampere’s law

(c) Faraday’s law

(d) Right hand rule

Answer
(d) Right hand rule

23. What will be the strength of magnetic field around a conductor choose which one is correct:

(a) Directly proportional to the square of distance from the conductor

(b) Same every where around the conductor

(c) Both (a) and (b)

(d) None of these

Answer
(b) Same every where around the conductor

24. A magnetic compass will be defected ifit is kept near a choose which one is correct:

(a) Charge at rest

(b) Charge in motion

(c) No change

(d) Both (a) and (b)

Answer
(b) Charge in motion

25. A current is passed through a straight conductor, the magnetic field produced around it. The magnetic lines of force are choose which one is correct:

(a) Straight

(b) Circular

(c) Parabolic

(d) None of these

Answer
(b) Circular

26. If a current carrying conductor is placed perpendicular to the magnetic field, it will experience a force choose which one is correct:

(a) 0

(b) F = BIL sin0

(c) F -BIL

(d) None of these

Answer
(b) F = BIL sin0

27. A magnetic field choose which one is correct:

(a) Exerts a force if a charge particle is moving perpendicular to the magnetic field

(b) Exerts a force if a charge particle is moving parallel to the magnetic field

(c) Never exerts a force on charged particle

(d) None of these

Answer
(a) Exerts a force if a charge particle is moving perpendicular to the magnetic field

28. Which one among the following material is most suitable for making core of electrometer choose which one is correct:

(a) Steel

(b) Cu — Ni alloy

(c) Air

(d) Soft iron

Answer
(d) Soft iron

29. The magnetic force experienced by a charge particle moving in a magnetic field will be minimum when it moves choose which one is correct:

(a) Parallel to magnetic field

(b) Anti-parallel to magnetic field

(c) Perpendicular to magnetic field

(d) None of these

Answer
(a) Parallel to magnetic field

30. The magnetic force experienced by a charge particle moving in a magnetic field will be maximum when it moves choose which one is correct:

(a) Parallel to magnetic field

(b) Anti-parallel to magnetic field

(c) Perpendicular to magnetic field

(d) None of these

Answer
(c) Perpendicular to magnetic field

31. Vector area is vector whose direction is choose which one is correct:

(a) Perpendicular to the surface element

(b) Parallel to the surface element

(c) At an angle of 450 to the surface element

(d) None of these

Answer
(a) Perpendicular to the surface element

32. If the magnetic field is directed along the normal to the area, then magnetic flux is choose which one is correct:

(a) Zero

(b) Maximum

(c) Minimum

(d) None of them

Answer
(b) Maximum

33. The unit of magnetic induction B is choose which one is correct:

(a) Coulomb

(b) Ampere

(c) Coulomb/ampere

(d) Weber/m2

Answer
(d) Weber/m2

34. Magnetic induction is defined as flux per unit area of the surface, which is choose which one is correct:

(a) Perpendicular to B

(b) Parallel to B

(c) Both (a) and (b)

(d) None of these

Answer
(a) Perpendicular to B

35. Magnetic flux density at any point due to a current carrying conductor can be computed from choose which one is correct:

(a) Newton’s law

(b) Coulomb’s law

(c) Ampere’s law

(d) Lenz’s law

Answer
(c) Ampere’s law

36. Amperean path is choose which one is correct:

(a) Circular path

(b) Closed path

(c) Rectangular path

(d) Any of above

Answer
(a) Circular path

37. is called choose which one is correct:

(a) Permeability of free space

(b) Proportional constant

(c) Permitivity of free space

(d) None of these

Answer
(a) Permeability of free space

38. A solenoid is a coil of wire, which is choose which one is correct:

(a) Short loosely wound cylindrical coil of wire

(b) Long tightly wound cylindrical coil of wire

(c) Both (a) and (b)

(d) None of these

Answer
(b) Long tightly wound cylindrical coil of wire

39. The magnetic field is uniform and stronger choose which one is correct:

(a) Outside the solenoid

(b) Inside the solenoid

(c) At the central part of the solenoid

(d) None of these

Answer
(c) At the central part of the solenoid

40. In the formula, B = gonl, where n represents choose which one is correct:

(a) Number of turns per unit length

(b) Number of turns per unit volume

(c) Number of turns per unit area

(d) All of above

Answer
(a) Number of turns per unit length

41. The magnetic field inside the solenoid can be increased by choose which one is correct:

(a) Increasing number of turns

(b) Decreasing current

(c) Increasing current

(d) Both (a) and (c)

Answer
(d) Both (a) and (c)

42. The permeability of free space is measured in choose which one is correct:

(a) wb A/m

(b) Am/wb

(c) wb/Am

(d) m/wbA

Answer
(c) wb/Am

43. The strength of magnetic field is measured in SI units choose which one is correct:

(a) Am/N

(b) Nm/A

(c) N/Am

(d) N

Answer
(c) N/Am

44. Nm/A is commonly called choose which one is correct:

(a) Gauss

(b) Volt

(c) Ampere

(d) Weber

Answer
(d) Weber

45. A long wire wound tightly on a cylindrical coil is called choose which one is correct:

(a) Toroid

(b) Slide wire bridge

(c) Potentiometer

(d) Solenoid

Answer
(d) Solenoid

46. If the length of the solenoid is doubled without changing the number of turns then magnetic field choose which one is correct:

(a) is not charged

(b) becomes half

(c) becomes double

(d) None of these

Answer
(b) becomes half

47. If there are n charge carriers per unit volume then the number of charge carriers in a segment of wire of length L and area A is choose which one is correct:

(a) AL/n

(b) n A/L

(c) n AL

(d) n VA

Answer
(c) n AL

48. The electron gun in cathode ray oscilloscope consists of choose which one is correct:

(a) Grid

(b) Three anodes

(c) Indirectly heated cathode

(d) All of the above

Answer
(d) All of the above

49. When the charge particle is projected at right angles to the magnetic field then force experienced will be choose which one is correct:

(a) F = qvB

(b) Minimum

(c) Zero

(d) None of these

Answer
(a) F = qvB

50. When the charge particle is projected in the direction parallel to the magnetic field, then force experienced will be choose which one is correct:

(a) qvB

(b) Maximum

(c) Zero

(d) None of these

Answer
(c) Zero

51. When an electric charge q is placed in an electric field, it will experienced a force choose which one is correct:

(a) At an angle 450 to the field

(b) Parallel to electric field

(c) Perpendicular to the field

(d) None of these

Answer
(b) Parallel to electric field

52. The current passing through the coil of galvanometer is directly proportional to choose which one is correct:

(a) Angle of deflection

(b) Magnetic field

(c) Number of turns

(d) Resistance of the coil

Answer
(a) Angle of deflection

53. Lorentz force means the force acting on a particle, which is choose which one is correct:

(a) Magnetic force only

(b) Electric force only

(c) Sum of electric and magnetic force

(d) None of these

Answer
(c) Sum of electric and magnetic force

54. By means of waveform displayed on the screen of CRO, we can measure choose which one is correct:

(a) Frequency of voltage

(b) Voltage

(c) Phase of voltage

(d) All of above

Answer
(d) All of above

55. When an electron enters at right angle to the magnetic field, the magnitude of velocity choose which one is correct:

(a) Remains constant

(b) Decreases

(c) Increases

(d) None of these

Answer
(a) Remains constant

56. When an electron is projected in a direction perpendicular to the lines of magnetic force, its path may be choose which one is correct:

(a) Circular

(b) Straight line

(c) Parabola

(d) None of these

Answer
(a) Circular

57. The e/m of an electron can be calculated if we know the value of choose which one is correct:

(a) Magnetic Field

(b) Velocity of electron

(c) Radius of circular path

(d) All of above

Answer
(d) All of above

58. In CRO, the output waveform of time base generator is choose which one is correct:

(a) Circular

(b) Square

(c) Sinusoidal

(d) Saw-toothed

Answer
(d) Saw-toothed

59. If the magnetic flux is expressed in weber, then the magnetic induction can be expressed as choose which one is correct:

(a) Weber/m

(b) Weber/m2

(c) Weber/m3

(d) m/Weber

Answer
(b) Weber/m2

60. Which one of the following is the unit of magnetic induction choose which one is correct:

(a) Gauss

(b) Dyne

(c) Ampere

(d) Newton

Answer
(a) Gauss

61. The earth magnetic field always has a vertical component except at the one among the following choose which one is correct:

(a) Magnetic pole

(b) Magnetic equator

(c) Both (a) and (b)

(d) None of these

Answer
(a) Magnetic pole

62. Magnetic field is a choose which one is correct:

(a) Vector quantity

(b) Scalar quantity

(c) Scalar as well as vector

(d) None of these

Answer
(a) Vector quantity

63. The magnetic field at a point due to current carrying conductor is directly proportional to which among the following choose which one is correct:

(a) Current flows through the conductor

(b) Distance from the conductor

(c) Resistance of the conductor

(d) Thickness of the conductor

Answer
(a) Current flows through the conductor

64. The direction of the magnetic field produced by a linear current is given by choose which one is correct:

(a) Joule’s law

(b) Ampere law

(c) Right hand rule

(d) None of the above

Answer
(c) Right hand rule

65. Two free parallel wires carrying currents in opposite direction choose which one is correct:

(a) Repel each other

(b) Attract each other

(c) Do not effect each other

(d) All Of above

Answer
(a) Repel each other

66. Saw toothed waveform means that its voltage choose which one is correct:

(a) Decreases linearly with time

(b) Increases linearly with time

(c) Increases linearly with time and then drops to zero

(d) None of these

Answer
(c) Increases linearly with time and then drops to zero

67. A current carrying conductor surrounded by choose which one is correct:

(a) Magnetic field

(b) Electrostatic field

(c) Gravitational field

(d) All of above

Answer
(b) Electrostatic field

68. The voltage applied across X-plats deflects the beam choose which one is correct:

(a) Vertically or the screen

(b) Horizontally on the screen

(c) Both (a) and (b)

(d) None of these

Answer
(b) Horizontally on the screen

69. The energy resides in a current carrying conductor in the form of what among the following choose which one is correct:

(a) Magnetic field

(b) Electrostatic field

(c) Gravitational field

(d) All of above

Answer
(a) Magnetic field

70. If a moving electron deflected side ways on passing through a certain region of space, can we predict the presence of a magnetic field choose which one is correct:

(a) No

(b) Yes

(c) Maximum

(d) None of above

Answer
(b) Yes

71. The magnetic force experienced by a charged particle moving in a magnetic field will be maximum when it moves choose which one is correct:

(a) Perpendicular to the field

(b) Parallel to the field

(c) Anti parallel to the field

(d) All of above

Answer
(a) Perpendicular to the field

72. A compass needle will be deflected if it is kept near choose which one is correct:

(a) Charged body in motion

(b) A negatively charged body at rest

(c) A positively charged body at rest

(d) none of the above

Answer
(a) Charged body in motion

73. Ampere based his circuital law on the findings of choose which one is correct:

(a) Ampere himself

(b) Laplace

(c) Biot-servant

(d) Maxwell

Answer
(c) Biot-servant

74. The total no of magnetic lines of force passing normally through a given area will be known ad choose which one is correct:

(a) magnetic flux

(b) flux density

(c) self induction

(d) mutual induction

Answer
(a) magnetic flux

75. In CRO, the output waveform of time base generator is choose which one is correct:

(a) Circular

(b) Square

(c) Sinusoidal

(d) Saw-toothed

Answer
(d) Saw-toothed

76. Which one of the following quantities can be replaced by magnetic induction choose which one is correct:

(a) Flux density

(b) Magnetic flux

(c) Magnetic field intensity

(d) All of above

Answer
(a) Flux density

77. Charge to mass ratio (e/m) of a charged particle is also called choose which one is correct:

(a) Specific force

(b) Specific charge

(c) Both (a) and (b)

(d) None of the above

Answer
(b) Specific charge

78. The SI unit of permeability go is choose which one is correct:

(a) Weber —m/A

(b) Weber/A.m

(c) Weber —A/m

(d) None of the above

Answer
(b) Weber/A.m

79. A long tightly wound cylindrical coil of wire is called choose which one is correct:

(a) Capacitor

(b) Resistance

(c) Inductor

(d) Solenoid

Answer
(d) Solenoid

80. The magnetic field at the middle of the solenoid is choose which one is correct:

(a) Uniform and strong

(b) Uniform

(c) Strong

(d) Weak

Answer
(a) Uniform and strong

81. The magnetic field out of the solenoid is choose which one is correct:

(a) Negligible weak

(b) Uniform

(c) Uniform and strong

(d) All of above

Answer
(a) Negligible weak

82. The grides in CRO is at choose which one is correct:

(a) Negative potential w.r.to anode

(b) Positive potential w.r.to anode

(c) Negative potential w.r.to cathode

(d) Both (a) and (b)

Answer
(c) Negative potential w.r.to cathode

83. In CRO, there are choose which one is correct:

(a) Power deflecting plates

(b) Two sets of deflecting

(c) Three sets of deflecting plats

(d) None of these

Answer
(b) Two sets of deflecting

84. Which one is suitable for circular trajectory of a charged particle choose which one is correct:

(a) Magnetic field

(b) Electric field

(c) Conservative field

(d) Gravitational field

Answer
(a) Magnetic field

85. The voltage applied across X-plats deflects the beam choose which one is correct:

(a) Vertically or the screen

(b) Horizontally on the screen

(c) Both (a) and (b)

(d) None of these

Answer
(b) Horizontally on the screen

86. One tesla is equal to choose which one is correct:

(a) I Gauss

(b) 104 Gauss

(c) 10 Gauss

(d) 10-4 Gauss

Answer
(b) 104 Gauss

87. Magnetic flux density at a point due to the current carrying conductor determined by choose which one is correct:

(a) Faraday’s law

(b) Ampere’s law

(c) Flemming’s law

(d) Gauss’s law

Answer
(b) Ampere’s law

88. The anode in CRO are at choose which one is correct:

(a) Lower potential w.r.t cathode

(b) Higher potential w.r. to cathode

(c) Same potential as cathode

(d) None of these

Answer
(b) Higher potential w.r. to cathode

89. The expression for torque acting on a current carrying coil placed in a uniform magnetic field is equal to choose which one is correct:

(a) = BIA cos

(c) = BIA sin

(b) = BA cos

(d) = IB cos

Answer
(a) = BIA cos

90. A device used for the measurement and detection of current is called choose which one is correct:

(a) Ammeter

(b) Galvanometer

(c) Voltmeter

(d) All of the above

Answer
(b) Galvanometer

91. In case of galvanometer, the magnitude of the deflecting torque is given as choose which one is correct:

(a) BINA cos

(b) BIN

(c) NIA cos

(d) none of above

Answer
(a) BINA cos

92. The sensitivity of the galvanometer can be increased by increasing the choose which one is correct:

(a) Area of the coil

(b) Strength of magnetic field

(c) Number of turns of the coil

(d) All of these

Answer
(d) All of these

93. Indirectly heated cathode means that the choose which one is correct:

(a) Filament heats the cathode

(b) Cathode heat, the filament

(c) Grid heats the filament

(d) None of these

Answer
(a) Filament heats the cathode

94. Cathode ray oscilloscope works by deflecting a beam of choose which one is correct:

(a) Positrons

(b) Electrons

(c) Protons

(d) Both electrons and protons

Answer
(b) Electrons

95. A sensitive galvanometer measures currents choose which one is correct:

(a) In milli amperes

(b) In nano amperes

(c) In amperes

(d) In divisions of angle of twist

Answer
(d) In divisions of angle of twist

96. A moving coil galvanometer can be converted into ammeter by connecting choose which one is correct:

(a) A low resistance in series

(b) A low resistance in parallel

(c) A high resistance in series

(d) None of these

Answer
(b) A low resistance in parallel

97. A galvanometer can be converted into a voltmeter by connecting a what among the following choose which one is correct:

(a) High resistance in series

(b) Low resistance in parallel

(c) High resistance in parallel

(d) None of these

Answer
(a) High resistance in series

98. CRO works by deflecting the beam of electron as they pass through choose which one is correct:

(a) Uniform magnetic field

(b) Uniform electric field between two sets of parallel plates

(c) Non-uniform magnetic field

(d) None of these

Answer
(a) Uniform magnetic field

99. The force which deflects the coil of the galvanometer is called choose which one is correct:

(a) Deflecting torque

(b) Ordinary torque

(c) Reflecting torque

(d) None of these

Answer
(a) Deflecting torque

100. The device used for displaying the waveform of given voltage is choose which one is correct:

(a) A.C generator

(b) Cathode ray oscilloscope

(c) D,C generator

(d) Galvanometer

Answer
(b) Cathode ray oscilloscope

101. The voltage applied across Y-plate deflects the beam choose which one is correct:

(a) Vertically on the screen

(b) Horizontally on the screen

(c) Both (a) and (b)

(d) None of these

Answer
(a) Vertically on the screen