NEET Physics Motional and Static EMI Applications of EMI MCQs Set A

Question:  A solenoid has 2000 turns wound over a length of 0.3 m. Its cross-sectional area is 1.2 × 10^–3 m². Around its central section a coil of 300 turns is wound. If an initial current of 2 A flowing in the solenoid is reversed in 0.25 s, the emf induced in the coil will be

a) 2.4 × 10^–2 V

b) 4.8 × 10^–2 V

c) 4.8 × 10^–4 V

d) 2.4 × 10^–4 V

Answer: 2.4 × 10^–2 V

Question: A straight conductor of length 2m moves at a speed of 20 m/s. When the conductor makes an angle of 30° with the direction of magnetic field of induction of 0.1 wbm2 then induced emf

a) 2V

b) 1V

c) 3V

d) 4V

Answer:  2V

Question:

a) 3V

b) 2.5V

c) 1.5V

d) 1V

Answer:  3V

Question:

a) 0.01 T

b) 0.1 T

c) 0.02 T

d) 0.50 T

Answer: 0.01 T

Question: A 10-meter wire is kept in east-west direction. It is falling down with a speed of 5.0 meter/second, perpendicular to the horizontal component of earth's magnetic field of 0.30 ×10^-4 weber/meter². The momentary potential difference induced between the ends of the wire will be

a) 0.0015 V

b) 0.015 V

c) 0.15 V

d) 1.5 V

Answer: 0.0015 V

Question: When current in a coil changes from 5 A to 2 A in 0.1 s, average voltage of 50 V is produced. The self - inductance of the coil is

a) 1.67 H

b) 3 H

c) 0.67 H

d) 6 H

Answer:  1.67 H

Question:  A coil of circular cross-section having 1000 turns and 4 cm² face area is placed with its axis parallel to a magnetic field which decreases by 10^–2 Wb m^–2 in 0.01 s. The e.m.f. induced in the coil is:

a) 400 mV

b) 200 mV

c) 4 mV

d) 0.4 mV

Answer: 400 mV

Question: When current i passes through an inductor of self inductance L, energy stored in it is 1/2. L i². This is stored in the

a) magnetic field

b) current

c) electric field

d) voltage

Answer:  magnetic field

Question: If N is the number of turns in a coil, the value of self inductance varies as

a) N²

b) N^–2

c) N

d) None of these

Answer: N²

Question:  Two coils of inductances L₁ and L₂ are linked such that their mutual inducatance is M. Then

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d) None of these

Answer:

Question:

a) 0.20 mH

b) 0.15 mH

c) 0.10 mH

d) 0.05 mH

Answer:  0.20 mH

Question:  A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by afactor 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) 8

b) 12

c) 16

d) 4

Answer:  8

Question:

a)

b)

c)

d) 1W

Answer:

Question:

a)

b)

c) Both

d) None of these

Answer:

Question:  A rod PQ of length L moves with a uniform velocity v parallel to a long straight wire carrying a current i, the end P remaining at a distance r from the wire. The emf induced across the rod is

a)

b)

c)

d)

Answer:

Question:

a) zero

b)

c)

d)

Answer: zero

Question:

a)

b)

c)

d)

Answer:

Question:

a) 0.27 A

b) 0.37 A

c) 1.0 A

d) 0.72 A

Answer: 0.27 A

Question: A six pole generator with fixed field excitation develops an e.m.f. of 100 V when operating at 1500 r.p.m. At what speed must it rotate to develop 120V?

a) 1800 r.p.m

b) 400 r.p.m

c) 1200 r.p.m

d) 1500 r.p.m

Answer: 1800 r.p.m

Question:  If the magnetic flux linked with a coil through which a current of x A is set up is y Wb, then the coefficient of self inductance of the coil is

a)

b)

c)

d)

Answer:

Question:  The self inductance associated with a coil is independent of

a) resistance of coil

b) time

c) current

d) induced voltage

Answer: resistance of coil

Question: The plane in which eddy currents are produced in a conductor is inclined to the plane of the magnetic field at an angle equal to

a) 90°

b) 180°

c) 0°

d) 45°

Answer: 90°

Question:  Eddy currents are produced when

a) A metal is kept in varying magnetic field

b) A metal is kept in the steady magnetic field

c) A circular coil is placed in a magnetic field

d) Through a circular coil, current is passed

Answer:  A metal is kept in varying magnetic field

Question:  When strength of eddy currents is reduced, as dissipation of electrical energy into heat depends on the ...A... of the strength of electrical energy into heat depends on the ...A... of the strength of electric current heat loss is substantially ...B ... .Here, A and B refer to

a) square, reduced

b) inverse, increased

c) cube, increase

d) inverse, decreased

Answer: square, reduced

Question: Certain galvanometers have a fixed core made of nonmagnetic metallic material, when the coil oscillates, ...A... generated in the core ...B... the motion and bring the coil to rest ...C... Here, A, B and C refer to

a) eddy currents, oppose, quickly

b) mechanical energy, oppose, long time

c) induced current, support, long time

d) induced emf, support, long time

Answer: eddy currents, oppose, quickly

Question: When the plane of the armature of a generator is parallel to the field. in which it is rotating

a) the flux linked with it is zero, while induced emf is maximum

b) flux linked is maximum while induced emf is zero.

c) both the flux and emf have their respective maximum values.

d) both the flux linked and induced emf in the coil are zero

Answer:  the flux linked with it is zero, while induced emf is maximum

Question:

a) Assertion is correct, reason is correct; reason is a correct explanation for assertion

b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

c) Assertion is correct, reason is incorrect

d) Assertion is incorrect, reason is correct.

Answer: Assertion is correct, reason is correct; reason is a correct explanation for assertion

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) remain the same

b) decrease

c) increase

d) None of these

Answer:  remain the same

Question:  The mutual inductance of a pair of coils, each of N turns, is M henry. If a current of I ampere in one of the coils is brought to zero in t second, the emf induced per turn in the other coil, in volt, will be

a)

b)

c)

d)

Answer:

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) 0.2 henry

b) 0.8 henry

c) 0.1 henry

d) 0.4 henry

Answer: 0.2 henry

Question: Two coils of self inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is

a) 4 mH

b) 16 mH

c) 6 mH

d) 10 mH

Answer:  4 mH

Question:  The mutual inductance of a pair of coils is 0.75 H. If current in the primary coil changes from 0.5 A to zero in 0.01 s, find average induced e.m.f. in secondary coil.

a) 37.5 V

b) 22.5 V

c) 12.5 V

d) 25.5 V

Answer: 37.5 V

Question: A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the e.m.f. induced in the wire is 2 V, the magnitude of the field in tesla is

a) 0.8

b) 2.5

c) 5

d) 2

Answer:  0.8

Question:

a) zero

b)

c)

d)

Answer: zero

Question:  The coefficient of self inductance of a solenoid is 0.18 mH. If a core of soft iron of relative permeability 900 is inserted, then the coefficient of self inductance will become nearly

a) 162 mH

b) 0.0002 mH

c) 5.4 mH

d) 0.006 mH

Answer: 162 mH

Question:  The inductance of a closed-packed coil of 400 turns is 8 mH. A current of 5 mA is passed through it. The magnetic flux through each turn of the coil is

a)

b)

c)

d)

Answer:

Question:  The figure shows a wire sliding on two parallel conducting rails placed at a separation I. A magnetic field B exists in a direction perpendicular to the plane of the rails. The force required to keep the wire moving at a constant velocity v will be

a) zero

b) evB

c) BIv

d) None of these

Answer: zero

Question:

a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

b) Assertion is correct, reason is correct; reason is a correct explanation for assertion

c) Assertion is incorrect, reason is correct.

d) Assertion is correct, reason is incorrect

Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion

Question:  A metallic square loop ABCD is moving in its own plane with velocity v in a unifrom magnetic field perpendicular to its plane as shown in figure. An electric field is induced

a) neither in AD nor in BC

b) in both AD and BC

c) in BC, but not in AD

d) in AD, but not in BC

Answer: neither in AD nor in BC

Question: A conductor of length 0.4 m is moving with a speed of 7 m/s perpendicular to a magnetic field of intensity 0.9 Wb/m². The induced e.m.f. across the conductor is

a) 2.52 V

b) 5.04 V

c) 25.2 V

d) 1.26 V

Answer: 2.52 V

Question:  A circular coil and a bar magnet placed nearby are made to move in the same direction. If the coil covers a distance of 1 m in 0.5. sec and the magnet a distance of 2 m in 1 sec, the induced e.m.f. produced in the coil is

a) zero

b) 0.5 V

c) 1 V

d) 2 V.

Answer:  zero

Question:

a) 2.07 × 10^–3 W

b) 3.14 × 10^–3 W

c) 1.23 × 10^–3 W

d) 1.80 × 10^–3 W

Answer: 2.07 × 10^–3 W

Question: A 100 millihenry coil carries a current of 1 ampere. Energy stored in its magnetic field is

a) 0.05 J

b) 0.1 J

c) 1 J

d) 0.5 J

Answer: 0.05 J

Question: Two solenoids of same cross-sectional area have their lengths and number of turns in ratio of 1 : 2 both. The ratio of self-inductance of two solenoids is

a) 1 : 2

b) 2 : 1

c) 1 : 4

d) 1 : 1

Answer:  1 : 2

Question:

a)

b)

c)

d)

Answer:

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) 8

b) 4

c) 12

d) 16

Answer:  8

Question:

a)

b)

c)

d)  None of these

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:  Charge Q is uniplane formly distributed on a thin insulating ring of mass m which is initially at rest. To what angular velocity will the ring be accelerated when a magnetic field B, perpendicular to the of the ring, is switched on?

a)

b)

c)

d)

Answer:

Question:  An L-shaped conductor rod is moving in transverse magnetic field as shown in the figure. Potential difference between ends of the rod is maximum if the rod is moving with velocity

a)

b)

c)

d)

Answer:

Question:  A square frame of side 10 cm and a long straight wire carrying current 1 A are in the plate of the paper. Starting from close to the wire, the frame moves towards the right with a constant speed of 10 ms^–1 (see figure). The e.m.f induced at the time the left arm of the frame is at x = 10 cm from the wire is

a)

b)

c)

d)

Answer:

Question:  A copper disc of radius 0.1 m rotated about its centre with 10 revolutions per second in a uniform magnetic field of 0.1 tesla with its plane perpendicular to the field. The e.m.f. induced across the radius of disc is

a)

b)

c)

d)

Answer:

Question:  A generator has an e.m.f. of 440 Volt and internal resistance of 4000 hm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is

a) 400 volt

b) 200 volt

c) 440 volt

d) 220 volt

Answer:  400 volt

Question:

a) 400 W

b) 441 W

c) 484 W

d) 369 W

Answer:  400 W

Question:  A rectangular loop PQRS, is pulled with constant speed into a uniform transverse magnetic field by a force F (as shown). E.m.f. induced in side PS and potential difference between points P and S respectively are (Resistance of the loop = r)

a)

b)

c)

d) zero, zero

Answer:

Question:

a)

b)

c)

d) None of these

Answer:

Question:

a) along –x direction

b) along +y direction

c) along +x direction

d) zero

Answer:  along –x direction

Question:  A conducting ring of radius l m kept in a uniform magnetic field B of 0.01 T, rotates uniformly with an angular velocity 100 rad s^–1 with its axis of rotation perpendicular to B. The maximum induced emf in it is

a)

b)

c)

d) None of these

Answer: