Q.166 The eddy current loss increase with increase in frequency because it is____.
A. proportional to frequency
B. proportional to the cube of frequency
C. proportional to the square of frequency
D. inversely proportional to the frequency
Ans.: C
Q.167 What is the unit of self inductance?
A. volt ampere
B. volt sec per ampere
C. joule per ampere
D. volt per ampere
Ans.: B
Q.168 what is the resultant inductance, if two inductors of inductance L each are connected in series with opposite magnetic fluxes?
A. 2L
B. 6L
C.0
D.L
Ans.: A
Q.169 Which of the following is not applications of eddy current?
A. Crystallography
B. induction furnace
C. Speedometer
D. Galvanometer
Ans.: A
Q.170 The voltage across the inductor is 5V , what will be the self inductance of coil when current changes from 3 to 2A in one millisecond?
A. 500 Henry
B. 50 Henry
C. 5000 Henry
D. 50000 Henry
Ans.: C
Q.171 A magnet is allowed to fall through a metal ring. During the fall what happen?
A. its acceleration is more than g
B. its acceleration is less than g
C. it acceleration is due to g
D. its acceleration is due to both g and magnetic field
Ans.: B
Q.172 what if induced emf of coil having 500 turns of square shape, each side 10 cm is placed normal to a magnetic field which is increasing at 1J/s.
A. 4 V
B. 3 V
C. 6 V
D. 5V
Ans.: D
Q.173 When eddy currents are produced?
A. rectangular coil is placed in electric field
B. a metal is kept in steady magnetic field
C. coil is placed in electric field
D. metal is placed in electric field
Ans.: B
Q.174 when a magnet is pushed in and out of a circular coil with frequency f. what will be the deflection in galvanometer?
A. Oscillation in deflection will seen clearly
B. constant deflection will be seen
C. no deflection will seen due to constant variation
D. small variation will observed
Ans.: A
Q.175 A coil of certain radius has 600 turns and a self inductance of 108 mH. What is self inductance of second similar coil of 500 turns?
A. 73 mH
B. 74 mH
C. 75 mH
D. 76 mH
Ans.: C
Q.176 The electromagnet is made of ____
A. steel core
B. soft iron core wrapped in a coil of fine wire with current flowing through it
C. iron core
D. copper bars
Ans.: B
Q.177 ___ used the principle of statically induced emf.
A. Battery
B. Generator
C. Transformer
D. Motor
Ans.: C
Q.178 If we lower the self inductance of a coil___
A. more will be the flux produced
B. less will be the flux produced
C. no change in the value of flux
D. less will be the weber
Ans.: B
Q.179 The coupling between the two magnetically coupled coil is said to be ideal if value of coefficient of coupling is ___.
A. 1
B. 1.5
C. 2
D. zero
Ans.: A
Q.180 what is the value of energy stored in magnetic field of solenoid 30 cm long and 3 cm diameter wound 1000 turns over it of wire carrying current is 10 A?
A. 0.55 J
B. 0.15 J
C. 0.015J
D. 1 J
Ans.: C