HSSC-II (Class-12) Solved Physics MCQs; Unit-13: Electromagnetism (Baluchistan Textbook Board, Quetta) With Verified Answers
1. The source of induced e.m.f.is
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
Induced e.m.f. produced depends upon the Relative speed between the bar magnet and 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
it is a special type of potential difference
4. The law of electromagnetic induction was introduced by
Faraday's Law of electromagnetic induction
5. According to Faraday's Law of electromagnetic induction, the induced e.m.f. depends upon
Methodical form of Faraday's Law of electromagnetic induction Ɛ = -N `\frac {Δф}{Δt}`
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}`
Lenz's law not only provided the direction of the induced current it also gives the principle of the law of conservation of Energy
L = `\frac {Ɛ}{∆I/∆t}` = `\frac {8V}{{2A}/{0.05 s}}` = 1.25 H
1 H = Wb A⁻¹ = V s A⁻¹ = kg m² s⁻² A⁻² [Wb= Weber, A=Ampere, V=Volt]
Ɛ = -vBl = 5 m s⁻¹ｘ 0.5 m ｘ 2 T = 5 V
Inductor stores magnetic potential energy in its magnetic field while a capacitor stores electric potential energy in its electric field
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Answer is D. `\frac {1}{2}`LI² Methodical form of Faraday's Law of electromagnetic induction Ɛ = -N `\frac {Δф}{Δt}`
6. Lenz's law of electromagnetic induction explains:
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 :
Lenz's law not only provided the direction of the induced current it also gives the principle of the law of conservation of Energy
8. The mutual inductance of two coils is maximum when the coils are
9. When 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
L = `\frac {Ɛ}{∆I/∆t}` = `\frac {8V}{{2A}/{0.05 s}}` = 1.25 H
10. The unit of inductance is
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
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?
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
The Energy stored is related to inductance and current
14. The working principle of an A.C. motor is
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15. The stator and the rotor of an A.C. motor are connected by a
There is a small gap between the stator and the rotor as known as the air gap
16.. Two phases A.C. contains
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17. A transformer works when we apply :
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18. The quantity that remains constant in a transformer is
Only frequency remains constant. all others can be varied.
19. The soft iron core is used in a transformer in order to
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20. Which relation is true for an ideal transformer?
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21. When a step-up transformer delivers high voltage then the current will be
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22. For long-distance electrical power transmission, we use
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23. Lamination is used in a transformer in order to
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