Electromagnetic Induction Multiple Choice Questions with Answers-01 (English)

1. Which circuit element(s) will oppose the change in circuit current ?
(A) Resistance only
(B) Inductance only
(C) Capacitance only
(D) Inductance and capacitance
Ans: B

2. A crack in the magnetic path of an inductor will result in
(A) unchanged inductance
(B) increased inductance
(C) zero inductance
(D) reduced inductance
Ans: D

3. A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by
(A) variation in coil current
(B) variation in voltage to the coil
(C) change of number of turns of coil
(D) the resistance of magnetic path
Ans: B

4. Higher the self-inductance of a coil,
(A) lesser its weber-turns
(B) lower the e.m.f. induced
(C) greater the flux produced by it
(D) longer the delay in establishing steady current through it
Ans: D

5. 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) initially increase and then decrease
Ans: B

6. Which of the following inductor will have the least eddy current losses ?
(A) Air core
(B) Laminated iron core
(C) Iron core
(D) Powdered iron core
Ans: A

7. Air-core coils are practically free from
(A) hysteresis losses
(B) eddy current losses
(C) both (A) and (B)
(D) none of the above
Ans: C

8. The magnitude of the induced e.m.f. in a conductor depends on the
(A) flux density of the magnetic field
(B) amount of flux cut
(C) amount of flux linkages
(D) rate of change of flux-linkages
Ans: D

9. 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
Ans: D

10. 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) the laminations are stacked vertically
Ans: B

11. The law that the induced e.m.f. and current always oppose the cause producing them is due to
(A) Faraday
(B) Lenz
(C) Newton
(D) Coulomb
Ans: B

12. Which of the following is not a unit of inductance ?
(A) Henry
(B) Coulomb/volt ampere
(C) Volt second per ampere
(D) All of the above
Ans: B

13. In case of an inductance, current is proportional to
(A) voltage across the inductance
(B) magnetic field
(C) both (A) and (B)
(D) neither (A) nor (B)
Ans: B

14. Which of the following circuit elements will oppose the change in circuit current ?
(A) Capacitance
(B) Inductance
(C) Resistance
(D) All of the above
Ans: B

15. The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as
(A) self-inductance
(B) mutual inductance
(C) series aiding inductance
(D) capacitance
Ans: A

16. 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 flux
(B) lies in a magnetic field
(e) cuts magnetic flux
(D) moves parallel to the direction of the magnetic field
Ans: C

17. Which of the following circuit element stores energy in the electromagnetic field ?
(A) Inductance
(B) Condenser
(C) Variable resistor
(D) Resistance
Ans: A

18. The inductance of a coil will increase under all the following conditions except
(A) when more length for the same number of turns is provided
(6) when the number of turns of the coil increase
(C) when more area for each turn is provided
(D) when permeability of the core increases
Ans: A

19. An open coil has
(A) zero resistance and inductance
(B) infinite resistance and zero inductance
(C) infinite resistance and normal inductance
(D) zero resistance and high inductance
Ans: B

20. Both the number of turns and the core length of an inductive coil are doubled.
Its self-inductance will be
(A) unaffected
(B) doubled
(C) halved
(D) quadrupled
Ans: B