Question: Core of an electromagnet should have____________?

• 1. low coercivity
• 2. high susceptibility
• 3. both of the above
• 4. none of the above

Question: Main causes of noisy solenoid are______________?

• 1. strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force
• 2. uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
• 3. both of above
• 4. none of the above

Question: Magnetism of a magnet can be destroyed by_____________?

• 1. heating
• 2. hammering
• 3. by inductive action of another magnet
• 4. by all above methods

Question: A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be nearly______________?

• 1. 50 N
• 2. 120 N
• 3. 240 N
• 4. 480 N

Question: A conductor 2 meters long moves at right angles to a magnetic field of flux density 1 tesla with a velocity of 12.5 m/s. The induced e.m.f. in the conductor will be____________?

• 1. 10 V
• 2. 15 V
• 3. 25V
• 4. 50V

Question: Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be_____________?

• 1. 6 H
• 2. 8 H
• 3. 12 H
• 4. 24 H

Question: Lenz’s law is a consequence of the law of conservation of__________?

• 1. induced current
• 2. charge
• 3. energy
• 4. induced e.m.f.

Question: In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling will be____________?

• 1. 2.0
• 2. 1.0
• 3. 0.5
• 4. zero

Question: 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___________?

• 1. 6 mH
• 2. 14 mH
• 3. 24 mH
• 4. 48 mH

Question: The self inductances of two coils are 8 mH and 18 mH. If the co-efficients of coupling is 0.5, the mutual inductance of the coils is______________?

• 1. 4 mH
• 2. 5 mH
• 3. 6 mH
• 4. 12 mH