Temporary magnets are used in______________?

A. Loud-speakers
B. Generators
C. Motors
D. All of the above

For which of the following materials the net magnetic moment should be zero ?

A. Diamagnetic materials
B. Ferrimagnetic materials
C. Antiferromagnetic materials
D. Antiferrimagnetic materials

Which of the following statements is correct ?

A. The conductivity of ferrites is better than ferromagnetic materials
B. The conductivity of ferromagnetic materials is better than ferrites
C. The conductivity of ferrites is very high
D. The conductivity of ferrites is same as that of ferromagnetic materials

Core of an electromagnet should have____________?

A. Low coercivity
B. High susceptibility
C. Both of the above
D. None of the above

Main causes of noisy solenoid are______________?

A. Strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force
B. Uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
C. Both of above
D. None of the above

Magnetism of a magnet can be destroyed by_____________?

A. Heating
B. Hammering
C. By inductive action of another magnet
D. By all above methods

Which of the following methods may be used to convert A.C. system to D.C ?

A. rectifiers
B. motor converters
C. motor-generator sets
D. rotary converters

A synchronous converter can be started______________?

A. By means of a small auxiliary motor
B. From ac. side as induction motor
C. From d.c. side as d.c. motor
D. Any of the above methods

Which of the following are the applications of D.C. system ?

A. battery charging work
B. arc welding
C. electrolytic and electro-chemical processes
D. arc lamps for search lights

In a single phase rotary converter the number of slip rings will be_____________?

A. Two
B. Three
C. Four
D. Six