## electrical

### Electromagnetic Induction MCQ Questions and Answers

1.
 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 Answer : A Explanation :
2.
 As per faraday’s law of electromagnetic induction, an e.m.f is induced in a conductor whenever it A Lies perpendicular to magnetic flux B Lies in a magnetic line C Cuts magnetic flux D Moves parallel to the direction of the magnetic field Answer : C Explanation :
3.
 Which of the following circuit elements stores energy in the electromagnetic filed? A Inductance B Condenser C Variable resistor D Resistance Answer : A Explanation :
4.
 The inductance of a coil will increase under all the following conditions excepts A When more length for the same number of turns is provided B 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 Answer : A Explanation :
5.
 Higher the self-inductance of the coil A Lesser its Webber-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 Answer : D Explanation :
6.
 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 same D Initially increase then decrease Answer : B Explanation :
7.
 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 Answer : B Explanation :
8.
 Both the number of turn and core length of an inductive coil are doubled. Its self-inductance will be A Unaffected B Doubled C Halved D Quadrupled Answer : B Explanation :
9.
 If current in a conductor increases then according to lenz’s law self-inductance voltage will A Aid the increasing current B Tends to decrease the amount of current C Produce current opposite to the increasing current D Aid the applied voltage Answer : C Explanation :
10.
 The direction of induced e.m.f can be found by A Laplace’s law B Lenz’s law C Fleming’s right hand rule D Kirchhoff’s voltage law Answer : B Explanation :
11.
 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 : C Explanation :
12.
 The magnitude of the induced e.m.f in a conductor depends upon 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 : D Explanation :
13.
 Mutually inductance between two magnetically-coupled coils depends upon 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 : D Explanation :
14.
 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 Answer : B Explanation :
15.
 The law that the induced e.m.f and current always oppose the cause producing them is due to A Faraday’s B Lenz C Newton D Coulomb Answer : B Explanation :
16.
 Which of the following is not a unit of inductance? A Hennery B Coulomb/volt ampere C Volt second/ampere D All of the above Answer : B Explanation :
17.
 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) Answer : B Explanation :
18.
 Which of the following circuit elements will oppose the change in circuit current? A Capacitance B Inductance C Resistance D All of the above Answer : B Explanation :
19.
 For a purely inductive circuit which of the following is true? A Apparent power is zero B Relative power is zero C Actual power of the circuit is zero D Any capacitance even if present in the circuit will not be charged Answer : C Explanation :
20.
 Which of the following is unit of inductance? A Ohm B Henry C Ampere turns D Weber/meters Answer : B Explanation :
21.
 An e.m.f of 16 volts is induced in a coil of inductance 4H. the rate of change of current must be A 64 A/s B 32 A/s C 16 A/s D 4 A/s Answer : D Explanation :
22.
 The core of the coil has a length of 200 mm. the inductance coil of 6 mH. If the core length is doubled, all other quantities, remaining the same, the inductance will be A 3 mH B 12 mH C 24 mH D 48 mH Answer : A Explanation :
23.
 The self-inductance of two coils are 8 mH. If the co-efficient of coupling is 0.5, the mutual inductance of the coil is A 4 mH B 5 mH C 6 mH D 12 mH Answer : C Explanation :
24.
 Two coil have inductance of 8 mH and 18mH and co-efficient of coupling of 0.5. if the two coils are connected in series aiding, the total inductance will be A 32 mH B 38 mH C 40 mH D 48 mH Answer : B Explanation :
25.
 A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400 turns, all other quantities ( area, length etc.) remaining the same, the inductance will be A 6 mH B 14 mH C 24 mH D 48 mH Answer : D Explanation :
26.
 Two coils have self-inductance of 10 h and 2 h, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be A 6 H B 8 H C 12 H D 24 H Answer : C Explanation :
27.
 In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling will be A 2.0 B 1.0 C 0.5 D Zero Answer : B Explanation :
28.
 The energy in joules stored in magnetic field of 0.15 h inductance with a 180 mA current will be A 2.43 B 2.43 x 10 -3 C 2.43 x 10 -6 D 2.43 x 10 -9 Answer : B Explanation :
29.
 A coil with negligible resistance has 50 V across it with 10 mA. The inductive reactance is A 50 ohms B 500 ohms C 1000 ohms D 5000 ohms Answer : D Explanation :
30.
 Lenz’s law is a consequence of the law of conversion of A Induced current B Charge C Energy D Induced e.m.f Answer : C Explanation :
31.
 The co-efficient of coupling between the air core coils depends upon A Self-inductance of two coils only B Mutual inductance of two coils only C Mutual inductance and self-inductance of two coils D None of the above Answer : C Explanation :
32.
 An average voltage of 10 v is induced in a250 turns solenoid as a result of a change in flux which occurs in 0.5 seconds. The total flux change is A 20 Wb B 2 Wb C 0.2 Wb D 0.02 Wb Answer : D Explanation :
33.
 A 500 turns solenoid develops an average induced voltage of 60 V. over what time interval must a flux change of 0.06 Wb occur to produce such a voltage? A 0.01 s B 0.1 s C 0.5 s D 5 s Answer : C Explanation :
34.
 Which of the following inductor will have the least eddy current losses? A Air core B Laminate iron core C Iron core D Powdered iron core Answer : A Explanation :
35.
 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 150 mH Answer : B Explanation :
36.
 Two 300 µH coils in series without mutual coupling have a total inductance of A 300 µH B 600 µH C 150 µH D 75 µH Answer : B Explanation :
37.
 Current charging from 8 A to 12 a in on second induced 20 volts in a coil. The value of inductance is A 5 mH B 10 mH C 5 H D 10 H Answer : C Explanation :
38.
 Which circuit element will oppose the change in circuit current? A Resistance only B Inductance only C Capacitance only D Inductance and capacitance Answer : B Explanation :
39.
 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 : D Explanation :
40.
 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 coils D The resistance of magnetic path Answer : B Explanation :
41.
 Which of the following statements is correct? A The inductance of a coil carrying a constant DC current will change the current into pulses B The inductance of a coil carrying a constant DC current will increase the current C The inductance of a coil carrying a constant DC current will not affect the current D The inductance of a coil carrying a constant DC current will decrease the current Answer : C Explanation :