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Electromagnetic Induction Quiz | Electromagnetic Induction Objective Type Questions and Answers

Questions
21 What is emf?
A Force
B Voltage
C Current
D Flux

Answer: Voltage
22 Find the strength of the magnetic field in a conductor 0.5m long moving with a velocity of 10m/s, inducing an emf of 20V if magnetic field, velocity and length of conductor are mutually perpendicular to each other.
A 1T
B 2T
C 3T
D 4T

Answer: 4T
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23 Find the length of a conductor which is moving with a velocity 0.4m/s in a magnetic field of 8T, inducing an emf of 20V if magnetic field, velocity and length of conductor are mutually perpendicular to each other.
A 50m
B 5m
C 6.25m
D 0.5m

Answer: 6.25m
24 The formula for induced emf if magnetic field, length and velocity of conductor all are mutually perpendicular is __________
A emf=B2l
B emf=Bil
C emf=Blv
D None of the above

Answer: emf=Blv
25 What is the consequence of motor effect?
A Current
B Voltage
C Electromagnetic induction
D All of the above

Answer: Electromagnetic induction
26 What happens to the current in a coil while accelerating a magnet inside it?
A Increases
B Decreases
C Remains constant
D Reverses

Answer: Increases
27 A crack in the magnetic path of an inductor will result in
A unchanged inductance
B increased inductance
C zero inductance
D reduced inductance

Answer: reduced inductance
28 Two 300 uH coils in series without mutual coupling have a total inductance of
A 300 uH
B 600 uH
C 150 uH
D None of these

Answer: 600 uH
29 A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is
A 3500 mH
B 350 mH
C 250 mH
D None of the Above

Answer: 350 mH
30 Current changing from 8 A to 12 A in one second induced 20 volts in a coil. The value of inductance is
A 5 mH
B 10 mH
C 5 H
D None Of The Above

Answer: 5 H
31 An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is
A 20 Wb
B 2 Wb
C 0.02 Wb
D None of the Above

Answer: 0.02 Wb
32 Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla.
A 100 N
B 400 N
C 600 N
D None of the above

Answer: 100 N
33 A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be nearly
A 50 N
B 120 N
C 240 N
D none of the above

Answer: 120 N
34 As per Faraday’s laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it
A lies perpendicular to the magnetic fluxe
B lies in a magnetic field
C cuts magnetic flux
D All of the above

Answer: cuts magnetic flux
35 Which of the following circuit element stores energy in the electromagnetic field ?
A Inductance
B Condenser
C Variable resistor
D None of these

Answer: Inductance
36 In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will
A increase
B decrease
C remain the same
D None of the above

Answer: decrease
37 If current in a conductor increases then according to Lenz’s law self-induced voltage will
A aid the increasing current
B tend to decrease the amount of cur-rent
C produce current opposite to the in-creasing current
D aid the applied voltage

Answer: produce current opposite to the in-creasing current
38 Air-core coils are practically free from
A hysteresis losses
B eddy current losses
C both (a) and (b)
D None of the above

Answer: both (a) and (b)
39 Mutually inductance between two magnetically-coupled coils depends on
A permeability of the core
B the number of their turns
C cross-sectional area of their common core
D all of the above

Answer: all of the above
40 A laminated iron core has reduced eddy-current losses because
A more wire can be used with less D.C. resistance in coil
B the laminations are insulated from each other
C the magnetic flux is concentrated in the air gap of the core
D None Of The Above

Answer: the laminations are insulated from each other

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