# 12th Class Physics Mcqs Chapter no 14 | Physics Mcqs For Class 12th Mcqs 2021 with answers pdf

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Chapter 14

ELECTROMAGNETISM

Encircle the most appropriate answer among the following options

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

(c) Coloumb

(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

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

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

(a) Lenz

(c) Oersted

(d) None of above

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

(a) Electric current

(b) Electric field

(c) Magnetic field

(d) None of above

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

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

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

(a) Magnetic flux

(b) Magnetic induction

(d) Electric 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

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

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

(a) Magnetic flux

(b) Permeability

(c) Magnetic force

(d) None of above

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

(a) volt/sec

(b) volt2/sec

(c) volt/sec2

(d) sec/volt

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

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

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

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

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

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

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

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

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

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

(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

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)

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

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

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

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

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

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

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

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

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

(a) Coulomb

(b) Ampere

(c) Coulomb/ampere

(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

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

36.       Amperean path is choose which one is correct:

(a) Circular path

(b) Closed path

(c) Rectangular path

(d)        Any of above

37.       o is called choose which one is correct:

(a) Permeability of free space

(b) Proportional constant

(c) Permitivity of free space

(d) None of these

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

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

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

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)

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

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

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

(a) Gauss

(b) Volt

(c) Ampere

(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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

(a) Capacitor

(b) Resistance

(c) Inductor

(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

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

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)

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

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

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

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

(a) I Gauss

(b) 104 Gauss

(c) 10 Gauss

(d) 10-4 Gauss

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

(b) Ampere’s law

(c) Flemming’s law

(d) Gauss’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

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

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

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

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

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

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

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

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

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

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

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

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

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