# MCQs for Physics Class 12 with Answers Chapter 6 Electromagnetic Induction

Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Electromagnetic Induction with answers provided here which is an important chapter in Class 12 Physics NCERT textbook. These MCQ for Class 12 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 12 Physics examination

## Chapter 6 Electromagnetic Induction MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Electromagnetic Induction provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. Whenever the flux linked with a circuit changes, there is an induced emf in the circuit. This emf in the circuit lasts
(a) for a very short duration
(b) for a long duration
(c) forever
(d) as long as the magnetic flux in the circuit changes.

D

Question. The area of a square shaped coil is 10–2 m2. Its plane is perpendicular to a magnetic field of strength 10–3 T. The magnetic flux linked with the coil is
(a) 10 Wb
(b) 10–5 Wb
(c) 105 Wb
(d) 100 Wb

B

Question. An area A = 0.5 m2 shown in the figure is situated in a uniform magnetic field B = 4.0 Wb/m2 and its normal makes an angle of 60° with the field. The magnetic flux passing through the area A would be equal to

(a) 2.0 weber
(b) 1.0 weber
(c) 3 weber
(d) 0.5 weber

B

Question. A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A magnetic induction B constant in time and space, pointing perpendicular and into the plane of the loop exists everywhere as in given figure. The current induced in the loop is

(a) Blv/R clockwise
(b) Blv/R anticlockwise
(c) 2 Blv/R anticlockwise
(d) zero.

D

Question. Inductance plays the role of
(a) inertia
(b) friction
(c) source of emf
(d) force

A

Question. A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because
(a) the magnetic field is constant.
(b) the magnetic field is in the same plane as the circular coil and it may or may not vary.
(c) the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably.
(d) there is a constant magnetic field in the perpendicular (to the plane of the coil) direction.

B

Question. When the current in a coil changes from 8A to 2A in 3 × 10–2 second, the emf induced in the coil is 2 volt. The self-inductance of the coil, in millihenry, is
(a) 1
(b) 5
(c) 20
(d) 10

D

Question. A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from
(a) the current source
(b) the magnetic field
(c) the lattice structure of the material of the rod
(d) the induced electric field due to the changing magnetic field

A

Question. The mutual inductance of two coils depends upon
(a) medium between coils
(b) separation between coils
(c) both on (a) and (b)
(d) none of (a) and (b)

C

Question. A square of side L meters lies in the X-Y plane in a region, where the magnetic field is given by B=Bo (2it+3tj+4kt)T, where Bo is constant. The magnitude of flux passing through the square is
(a) 2 Bo L2 Wb
(b) 3 Bo L2 Wb
(c) 4 Bo L2 Wb
(d) √29 BL2 Wb

C

Question. A loop, made of straight edges has six corners at A(0, 0, 0), B(L, O, 0), C(L, L, 0), D(0, L, 0) E(0, L, L) and F(0, 0, L). A magnetic field B=Bo (it+kt)T is present in the region. The flux passing through the loop ABCDEFA (in that order) is
(a) Bo L2 Wb
(b) 2 Bo L2 Wb
(c) 2 BL2 Wb
(d) 4 Bo L2 Wb

B

Question. An emf is produced in a coil, which is not connected to an external voltage source. This can be due to
(a) the coil being in a time varying magnetic field.
(b) the coil moving in a time varying magnetic field.
(c) the coil moving in a constant magnetic field.
(d) the coil is stationary in external spatially varying magnetic field, which does not change with time.

A, B, C

Question. A magnet is dropped with its north pole towards a closed circular coil placed on a table then
(a) looking from above, the induced current in the coil will be anti-clockwise.
(b) the magnet will fall with uniform acceleration.
(c) as the magnet falls, its acceleration will be reduced.
(d) no current will be induced in the coil.

A

Question. A cylindrical bar magnet is rotated about its axis (Figure given alongside). A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then

(a) a direct current flows in the ammeter A.
(b) no current flows through the ammeter A.
(c) an alternating sinusoidal current flows through the ammeter A with a time period T=2π/ω.
(d) a time varying non-sinusoidal current flows through the ammeter A.

B

Question. A copper ring is held horizontally and a magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is
(a) equal to that due to gravity
(b) less than that due to gravity
(c) more than that due to gravity
(d) depends on the diameter of the ring and the length of the magnet

B

Question. There are two coils A and B as shown in the figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counter clockwise. B is kept stationary when A moves. We can infer that

(a) there is a constant current in the clockwise direction in A.
(b) there is a varying current in A.
(c) there is no current in A.
(d) there is a constant current in the counterclockwise direction in A.

D

Question. Same as the above problem except the coil A is made to rotate about a vertical axis refer to the figure. No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counterclockwise and the coil A is as shown at this instant, t = 0, is

(a) constant current clockwise.
(b) varying current clockwise.
(c) varying current counterclockwise.
(d) constant current counterclockwise.

A

Question. Lenz’s law is essential for
(a) conservation of energy
(b) conservation of mass
(c) conservation of momentum
(d) conservation of charge

A

Question. The self inductance L of a solenoid of length l and area of crosssection A, with a fixed number of turns N increases as
(a) l and A increase.
(b) l decreases and A increases.
(c) l increases and A decreases.
(d) both l and A decrease.

B

Question. A thin circular ring of area A is held perpendicular to a uniform magnetic field of induction B. A small cut is made in the ring and a galvanometer is connected across its ends in such a way that the total resistance of the circuit is R. When the ring is suddenly squeezed to zero area, the charge flowing through the galvanometer is
(a) BR/A
(b) AB/R
(c) ABR
(d) B2A/R3

B

Question. Eddy currents are produced when
(a) a metal is kept in varying magnetic field
(b) a metal is kept in steady magnetic field
(c) a circular coil is placed in a magnetic field
(d) through a circular coil, current is passed

A

Question. An inductor may store energy in
(a) its electric field
(b) its coils
(c) its magnetic field
(d) both in electric and magnetic fields

C

Question. If N is the number of turns in a coil, the value of self inductance varies as
(a) N0
(b) N
(c) N2
(d) N–2

C

Question. A coil having an area A0 is placed in a magnetic field which changes from B0 to 4 B0 in time interval t. The e.m.f. induced in the coil will be
(a) 3A0 B0 / t
(b) 4A0 B0 / t
(c) 3B0 /A0t
(d) 4A0 / B0t

A

Question. An electron moves along the line PQ which lies in the same plane as a circular loop of conducting wire as shown in figure. What will be the direction of the induced current in the loop ?
(a) Anticlockwise
(b) Clockwise
(c) Alternating
(d) No current will be induced

A

Question. Induced emf in the coil depends upon
(a) conductivity of coil
(b) amount of flux
(c) rate of change of linked flux
(d) resistance of coil

C

Question. Two identical coaxial circular loops carry current i each circulating in the clockwise direction. If the loops are approaching each other, then
(a) current in each loop increases
(b) current in each loop remains the same
(c) current in each loop decreases
(d) current in one-loop increases and in the other it decreases

C

Question. According to Faraday’s law of electromagnetic induction
(a) electric field is produced by time varying magnetic flux.
(b) magnetic field is produced by time varying electric flux.
(c) magnetic field is associated with a moving charge.
(d) None of these

A

Question. Two solenoids of same cross-sectional area have their lengths and number of turns in ratio of 1 : 2. The ratio of self-inductance of two solenoids is
(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 1 : 4

B

Question. The back e.m.f. in a d.c. motor is maximum, when
(a) the motor has picked up max speed
(b) the motor has just started moving
(c) the speed of motor is still on the increase
(d) the motor has just been switched off

A

Question. Which of the following units denotes the dimension ML2/Q2 , where Q denotes the electric charge?
(a) Wb/m2
(b) henry (H)
(c) H/m2
(d) weber (Wb)

B

Question. The mutual inductance between two coils depends on
(a) medium between the coils
(b) separation between the two coils
(c) orientation of the two coils
(d) All of the above

D

Question. A small square loop of wire of side l is placed inside a large square loop of side L (L >> l ). The loop are coplanar and their centres coincide. The mutual inductance of the system is proportional is

B

Question. If coefficient of self induction of a coil is 1 H, an e.m.f. of 1V is induced, if
(a) current flowing is 1A
(b) current variation rate is 1 As–1
(c) current of 1A flows for one sec.
(d) None of these

B

Question. As a result of change in the magnetic flux linked to the closed loop shown in the figure, an e.m.f. V volt is induced in the loop.

The work done (in joule) in taking a charge Q coulomb once along the loop is
(a) QV
(b) 2QV
(c) QV/2
(d) zero

A

Question. The total charge induced in a conducting loop when it is moved in a magnetic field depend on
(a) the rate of change of magnetic flux
(b) initial magnetic flux only
(c) the total change in magnetic flux
(d) final magnetic flux only

C

Question. Lenz’s law is consequence of the law of conservation of
(a) energy
(b) momentum
(c) charge
(d) mass

A

Question. Fig shown below represents an area A = 0.5 m2 situated in a uniform magnetic field B = 2.0 weber/m2 and making an angle of 60º with respect to magnetic field.

The value of the magnetic flux through the area would be equal to
(a) 2.0 weber
(b) 3 weber
(c) 3 / 2 weber
(d) 0.5 weber

D

Question. When the current in a coil changes from 2 amp. to 4 amp. in 0.05 sec., an e.m.f. of 8 volt is induced in the coil. The coefficient of self inductance of the coil is
(a) 0.1 henry
(b) 0.2 henry
(c) 0.4 henry
(d) 0.8 henry

B

Question. If a current increases from zero to one ampere in 0.1 second in a coil of 5 mH, then the magnitude of the induced e.m.f. will be
(a) 0.005 volt
(b) 0.5 volt
(c) 0.05 volt
(d) 5 volt

C

Question. In the figure the flux through the loop perpendicular to the plane of the coil and directed into the paper is varying according to the relation f = 6t2 + 7t + 1 where f is in milliweber and t is in second. The magnitude of the emf induced in the loop at t = 2 s and the direction of induce current through R are

(a) 39 mV; right to left
(b) 39 mV; left to right
(c) 31 mV; right to left
(d) 31 mV; left to right

D

Question. Magnetic flux f in weber in a closed circuit of resistance 10W varies with time f (sec) as f = 6t2 – 5t + 1. The magnitude of induced current at t = 0.25s is
(a) 0.2 A
(b) 0.6 A
(c) 1.2 A
(d) 0.8 A

A

Question. The current in a coil of L = 40 mH is to be increased uniformly from 1A to 11A in 4 milli sec. The induced e.m.f. will be
(a) 100 V
(b) 0.4 V
(c) 440 V
(d) 40 V

A

Question. A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its side. A magnetic induction B constant in time and space, pointing perpendicular and into the plane of the loop exists everywhere.

D

Question. In fig., final value of current in 10Ω resistor, when plug of key K is inserted is

D

Question. A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by a factor 2 and the number of turns per unit length of the coil remains the same, self-inductance of the coil increases by a factor of
(a) 4
(b) 8
(c) 12
(d) 16

B

Question. In a circuit given in figure 1 and 2 are ammeters. Just after key K is pressed to complete the circuit, the reading is

(a) zero in both 1 and 2
(b) maximum in both 1 and 2
(c) zero in 1 and maximum in 2
(d) maximum in 1 and zero in 2

C

Question. A square metal loop of side 10 cm and resistance 1 Ω is moved with a constant velocity partly inside a uniform magnetic field of 2 Wbm–2, directed into the paper, as shown in the figure. The loop is connected to a network of five resistors each of value 3Ω. If a steady current of 1 mA flows in the loop, then the speed of the loop is

(a) 0.5 cms–1
(b) 1 cms–1
(c) 2 cms–1
(d) 4 cms–1

C

Question. Consider the situation shown. The wire AB is sliding on fixed rails with a constant velocity. If the wire AB is replaced by semi-circular wire, the magnitude of induced e.m.f. will

(a) increase
(b) decrease
(c) remain the same
(d) increase or decrease depending on whether the semicircle buldges towards the resistance or away from it.

C

Question. Same as problem 4 except the coil A is made to rotate about a vertical axis (figure). No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counter-clockwise and the coil A is as shown at this instant, t = 0, is
(a) constant current clockwise
(b) varying current clockwise
(c) varying current counter clockwise
(d) constant current counter clockwise

A

#### Fill in the Blanks

Question. _________________ particles radiate electromagnetic waves.

Accelerated charged

Question. The orderly distribution of electromagnetic radiations according to their frequency or wavelength is called _________________.

electromagnetic spectrum

Question. The shortest wavelength radio waves are called _________________.

micro-waves

Question. Electromagnetic waves are not _________________ by electric and magnetic waves.

deflected

Question. The displacement current is precisely equal to the conduction current, when the two are present in different parts of the circuit. These currents are individually discontinuous, but the two currents together posses the property of _________________ through any closed circuit.

continuity

Question. The current which comes into play in the region, whenever the electric field and hence the electric flux is changing with time is called _________________.

displacement current

Question. The _________________ of electromagnetic waves does not change when it goes from one medium to another but its wavelength changes.

frequency

Question. In case of electromagnetic wave, the vibrating electric field vector ( E ) and magnetic field vector ( B ) are mutually perpendicular to each other and both are perpendicular to the direction of _________________.

propagation

Question. Ozone layer in the atmosphere plays a protective role, and hence its depletion by _____________ gas is a matter of international concern.

chlorofluorocarbons (CFCs)

Question. Electromagnetic wave is _________________ in nature as the electric and magnetic fields are perpendicular to each other and to the direction of propagation of the wave.