1: The value of induced e.m.f in a coil of “N” number of turns depends upon:

A. Strengthof magnetic field

B. Speed at which magnet is moved towards or away from coil

C. No. of turns of coil

D. Allof these

2: A bar magnet of magnetic field 2T is made to move towards a coil having a galvanometer with a speed of 4 ms-1 such that galvanometer shows a

deflection “q1”. Now if the same bar magnet is made to move away from same coil with same speed and galvanometer shows deflection “q2” then what is true?

A. q1=q2 and both deflections are in same direction

B. q1<q2and both deflections are in same direction

C. q1>q2and both deflections are in opposite directions

D. q1=q2 but both deflections are in opposite direction

3: With reference to the Q.2 if only B is doubled and bar is only made to move towards coil with a speed of 4 ms-1 then:

A. Inducede.m.f becomes half

B. Induced e.m.f remains same

C. Induced e.m.f is doubled

D. None of these

4: With reference to the Q.2 if both B and speed of bar magnet are doubled then:

A. Induced e.m.f becomes quadrupled

B. Induced e.m.f remains same

C. Induced e.m.f is doubled

D. None of these

5: With reference to Q.2 if only number of turns of coil are doubled then: A. Inducede.m.f becomes half

B. Induced e.m.f remains same

C. Induced e.m.f is doubled

D. None of these

6: The relation for motional e.m.f can be written as: A. e = -vBLcos(90°-q)           

B. e = -vBLsinq

C. e = +vBLsinq                            

D. Both “A” & “B”

7: If a conductor is moved across a B such that q=90° then induced emf:

A. Is a maximum                                                    

B. Is zero

C. e = -vBL                                                        

D. Both “A” and “C”

8: At what angle when a rod is moved in a uniform B such that induced emf becomes half of it’s maximum?

A. 30°                                                                         

B. 45°

C. 60°                                                                         

D. 90°

9: According to Lenz’s law the direction of induced current is such that it:

A. Decreases flux if it is increasing

B. Opposes the cause which produces it

C. Increases flux if it is decreasing

D. Allof these

10: The cause of induced emf is:

A. Rateof change of magnetic flux

B. Decrease in flux

C. Increase in flux

D. Change in flux

11: If we take away north-pole of a bar magnet from a coil then the end of coil facing north-pole act as:

A. A north pole

C. May be north or south

B. A south pole

D. No pole will be induced

12: Which of the following is true about dependence upon resistance of the coil in which e.m.f is generated?

A. Only induced current depends upon resistance of coil

B. Only emf depends upon resistance of coil

C. Both emf and induced current depends upon resistance of coil

D. Can’t be predicted

14: Considering the statement of Q # 13 what is true about the acceleration of bar magnet while coming down?

A. a=g                              

B. a<g

C. a<g                                                                

D. a=0

15: Considering the figure of Q.13 if the coil is complete and does not have cut in it then:

A. Onlyemf will be induced

B. Only current will be induced

C. Both emf and current will be induced in it

D. Nothing will be induced

16: Considering the statement of Q.15 what is true about the acceleration produced in the bar magnet while falling downwards?

A. a=g                                                                    

B. a>g

C. a<g                                                                    

D. a=0

18: To measure the earth quakes, the instrument used is:

A.Barometer

C. Manometer

B. Venturimeter

D. Seismometer

19: The emf induced when a conductor is moved in a stationary magnetic field in such a way that flux linking it changes in magnitude, is called:

A. Staticallyinduced emf

B. Dynamically induced emf

C. Acceleratingemf

D. None of these

20: Basic component / components of AC – Motor is / are:

A.Stator                                  

B. Steel core

C. Rotor                                                                    

D. Both A and C

21: The basic working principle of an A.C generator is:

A. Toconvert mechanical energy into electrical energy

B. Toconvert electrical energy into mechanical energy

C. Mutual induction

D. Farday’s law of electromagnetic induction

22: The basic objective of an A.C generator is:

A. Toconvert mechanical energy into electrical energy

B. Toconvert electrical energy into mechanical energy

C. Mutual induction

D. Farday’s law of electromagnetic induction

23: The working principle of a transformer is:

A. Toconvert mechanical energy into electrical energy

B. Toconvert electrical energy into mechanical energy

C. Mutual induction

D. Farday’s law of electromagnetic induction

24: The basic objective of a transformer is:

A. Toincrease A.C voltage

C. Todecrease A.C voltage

B. Toalter A.C voltage

D. Toalter D.C voltage

25: What is the coefficient of mutual inductance, when the magnetic flux changes by 2´10-2 Wb, and change in current is 0.01 A?

A. 2H                  

B. 3H C. ½ H                                                      

D. Zero

26: The relation for e.m.f A. e =e° sinq produced by an A.C generator is:

B.e = NwABsinq

C. Both “A” and “B”                              

D. None of these

27: The maximum e.m.f induced by an A.C generator which has only one turn is:

A. NwAB                                                     

B. NAB

C. wAB                                                        

D. None of these

28: Step-up transformer has a transformation ratio of 3:2.What is the voltage in secondary, if voltage in primary is 30 V?

A. 45 V                                             

B. 15V

C. 90 V                                                                        

D. 300V

29: Eddy current is produced when:

A. A metal is kept in varying magnetic field

B. Ametal is kept in steady magnetic field

C. Acircular coil is placed in a steady magnetic field

D. A current is passed through a circular coil

30: The relation for back induced e.m.f in A. IR =V -eback
A. motor is:

B. IR=eback –V

C. V =eback +IR                                                         

D. Both “A” and “C”

31: The normal running current of motor is than / to overload current:

A.Greater

C. Less

B. Equal

D. Can’t be predicted

32: A motor is run by a battery of 24 volts. The coil of motor has resistance of 2W. It develops a back emf of 22.5 volts when driving the load at normal speed. What is starting current of motor?

A. 0.75 A

C. 12A

B. 6A

D. None of these

33: A coil of 100 turns is linked by a flux of 20 mWb. If this flux is reversed in 4 ms, the emf induced is:

A. 1000 V C. 2000 V

B. 3000 V

D. 4000 V

35: An A.C generator operating at 50Hz has a coil of 200 turns. The coil has an area of 120 cm2. What should be the angular frequency of coil to have a maximum emf of 240V?

A. 31.43 rad s-1

C. 314.3 rad s-1

B. 3.14 rad s-1

D. 100 rad s-1

36: The coil of motor is most likely to burn if: A. Motorgets over loaded

B. Back emf decreases

C. Maximum current is drawn from source D. Allof these

37: Amotor draws minimum current from the source when:

A. Motorhas maximum speed of rotation

B. Back emf is maximum

C. Rate of change of flux is maximum

D. Allof these

38: A step-up transformeris the one which:

A. Increases voltage level

B. Keeps power level

C. Decreases current level

D. All of these