In mercury arc rectifiers having grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as

In which of the following equipment direct current is needed?

A. Telephones

B. Relays

C. Time switches

D. All of the above

Mercury, in arc rectifiers, is chosen for cathode because

A. Its ionization potential is relatively low

B. Its atomic weight is quite high

C. Its boiling point and specific heat are low

D. All of the above

It is the_______of the transformer on which the magnitude of angle of overlap depends.

A. resistance

B. capacitance

C. leakage reactance

D. any of the above

Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required?

A. Motor-generator set

B. Motor converter

C. Rotary converter

D. Mercury arc rectifier