12th Class Physics MCQs Preparation 2022 and Onwards (Unit: Electromagnetic Induction: Set-1 (30 MCQs)) for National MDCAT, ECAT, FPSC, PPSC, JOB Exam, Physics Lecturer, SSC, HSSC (F.Sc.), BS, MS Exams NTS, ETS, etc..



1. The source of induced e.m.f.is




... Answer is D. Relative motion between magnet and coil
induced e.m.f. can be generated either by generator effects (by relative motion between changing magnet field and the conductor) or by transformer effect ( by changing the magnetic field B)


2. When the coil and a bar magnet are placed very close to each other than the value of their induced e.m.f. will be




... Answer is D. Zero
Induced e.m.f. produced depends upon the Relative speed between the bar magnet and the coil. No, induce e.m.f is produced when they are stationary no matter how close they are to each other.


3. The unit of induced e.m.f.is




... Answer is B. Volt
it is a special type of potential difference​


4. The law of electromagnetic induction was introduced by




... Answer is B. Faraday
Faraday's Law of electromagnetic induction


5.  According to Faraday's Law of electromagnetic induction, the induced e.m.f. depends upon




... Answer is D. Rate of change of magnetic flux
Methodical form of Faraday's Law of electromagnetic induction Ɛ = -N `\frac {Δф}{Δt}`


6. Lenz's law of electromagnetic induction explains:




... Answer is C. Direction of induced e.m.f..
Lenz's law of electromagnetic induction state as " the direction of the induced current is always such as to oppose the cause (direction of the action) that produces the induced current" its mathematical form is the same as Faraday's Law of electromagnetic induction that is Ɛ = -N `\frac {Δф}{Δt}`


7. Lenz's law is related to the law of conservation of :




... Answer is B. Energy
Lenz's law not only provided the direction of the induced current it also gives the principle of law of conservation of Energy 


8. The mutual inductance of two coils is maximum when the coils are




... Answer is A. Parallel to each other.


9. When a current changes in a coil from 4 A to 6 A in 0.05 s and it induces an e.m.f. of 8V. The co-efficient of self-inductance is




... Answer is A. 0.1H
L = `\frac {Ɛ}{∆I/∆t}` = `\frac {8V}{{2A}/{0.05 s}}` = 1.25 H


10. The unit of inductance is




... Answer is C. Henry
1 H = Wb A⁻¹ = V s A⁻¹ = kg m² s⁻² A⁻² [Wb= Weber, A=Ampere, V=Volt]


11. A conducting rod of length 0.5 m moves in a magnetic field of magnitude 2 T with velocity 5 m s⁻¹. the e.m.f. induced in the moving rod is




... Answer is A. 5 V
Ɛ = -vBl = 5 m s⁻¹ｘ 0.5 m ｘ 2 T = 5 V


12. Which one of the following devices stores magnetic potential energy in its magnetic field?




... Answer is C. Inductor
Inductor stores magnetic potential energy in its magnetic field while a capacitor stores electric potential energy in its electric field


13. At constant inductance of 'L' henry, the energy stored in a magnetic field is

... Answer is D. `\frac {1}{2}`LI²
The Energy stored is related to inductance and current


14.  The working principle of an A.C. motor is




... Answer is B. Mutual induction
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15. The stator and the rotor of an A.C. motor are connected by a




... Answer is D. No physical connection between them
There is a small gap between the stator and the rotor as known as the air gap


16.. Two phases A.C. contains




... Answer is C. Three wires two stators
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17. A transformer works when we apply :




... Answer is A. A.C. voltage
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18. The quantity that remains constant in a transformer is




... Answer is D. Frequency
Only frequency remains constant. all others can be varied.


19. The soft iron core is used in a transformer in order to




... Answer is A. Enhance the magnetic flux
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20. Which relation is true for an ideal transformer?




... Answer is C. Input power = output power
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21. When a step-up transformer delivers high voltage then the current will be




... Answer is B. Decreased
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22. For long-distance electrical power transmission, we use




... Answer is D. Smaller current and higher voltage
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23. Lamination is used in a transformer in order to




... Answer is D. Minimize eddy current
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24. In Fleming's left-hand rule thumb always represents the direction of




... Answer is D. Mechanical force
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25.  The field at any point on the axis of a current-carrying coil will be




... Answer is B. Parallel to the axis.
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26. When a coil rotated in a magnetic field the induced current in it




... Answer is A. continuously changes
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27. In A.C generator increasing the number of turns in the coil :




... Answer is C. increases the Electromotive force (e.m.f.)
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28. The device in which induced e.m.f. is statically induced e.m.f. is




... Answer is A. transformer
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29. What is the coefficient of mutual inductance, when the magnetic flux changes by 2 ｘ 10⁻² Wb, and the change in current is 0.01 A?




... Answer is A. 2H
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30. The induced e.m.f. in a coil is proportional to




... Answer is B. rate of change of magnetic flux through the coil
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