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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: 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: A

Question.  The self inductance associated with a coil is independent of
(a) resistance of coil
(b) time
(c) current
(d) induced voltage

Answer: A

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: A

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

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A

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: A