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Free download in PDF Electromagnetic Induction Objective Type Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like IIT-JEE, AIIMS etc. These short solved questions or quizzes are provided by Gkseries.
(21)
What is emf?
[A]
Force
[B]
Voltage
[C]
Current
[D]
Flux
(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
(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
(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
(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
(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
(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
(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
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
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
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
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
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
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
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
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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