Q.181 According to Faraday’s law of electromagnetic induction an emf is induced in a conductor when
A. it lies in an electric field
B. it cuts the magnetic flux
C. it lies in magnetic field
D. it moves parallel to magnetic field
Ans.: B
Q.182 An open coil has___
A. infinite resistance and zero inductance
B. infinite resistance and infinite inductance
C. zero resistance and zero inductance
D. zero resistance and infinite inductance
Ans.: A
Q.183 The magnitude of statically induced emf depend on__
A. flux magnitude
B. coil reactance
C. shape of coil
D. rate of change of flux
Ans.: D
Q.184 Consider two identical circular loops A and B of wire are lying on a table without touching each other. Loop A carries a current which increases with time. What response in loop B?
A. is attracted by loop A
B. is repelled by loop A
C. remains stationary
D. move forth and back
Ans.: B
Q.185 By what way the magnetic field strength of an air core coil can be increased?
A. by increasing the core cross sectional are
B. by increasing current strength
C. by increasing number of turns
D. none of the above
Ans.: A
Q.186____coil are almost free from eddy current and hysteresis loss.
A. solid iron core
B. solid copper core
C. air core
D. all of the above
Ans.: A
Q.187 The coil has 100 turns and inductance of the coil is 0.15 H. What will be the magnetic flux of the coil when 4 a current passed through it?
A. 2 mwb
B. 4 mwb
C. 8 mwb
D. 6 mwb
Ans.: D
Q.188 which of the following inductors will have the least eddy current loss?
A. laminated iron core
B. Air core
C. Iron core without laminations
D. all of the above
Ans.: B
Q.189 what it time constant of a coil at a certain current the energy stored in an iron cored coil is 1000 J and its copper loss is 2000 watt?
A. 2.0
B. 3.0
C. 1.0
D.0.1
Ans.: C
Q.190 The emf induced in a coil due to relative motion of a magnet is independent of ____.
A. number of coil turns
B. coil resistance
C. pole strength of the magnet
D. magnetic induction
Ans.: B
Q.191 If a copper conductor is moved across a magnetic field___.
A. no changes
B. copper conductors becomes magnet
C. a current will be induced in the wire
D. a voltage will be induced in the wire
Ans.: D
Q.192 which of the following equation is correct of energy stored in inductor?
A. LI2/2
B. LI2
C. 2L/I2
D. inductor never stored energy
Ans.: A
Q.193 A dynamo converts
A. chemical energy into electrical energy
B. mechanical energy into electrical energy
C. photon energy into electrical energy
D. wind energy into mechanical energy
Ans.: B
Q.194 A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then____
A. an emf will induced
B. a current will be induced
C. no current will be induced in the coil
D. can’t defined
Ans.: C
Q.195 Core of electromagnet should have__.
A. high susceptibility
B. low coercivity
C. high retentivity
D. Both A and B
Ans.: D