In a mercury arc rectifier positive ions are attracted towards______________?

A. Anode
B. Cathode
C. Shell bottom
D. Mercury pool

In which of the following equipment direct current is needed ?

A. Telephones
B. Relays
C. Time switches
D. All of the above

Which of the following AC. motors is usually used in large motor-generator sets?

A. Synchronous motor
B. Squirrel cage induction motor
C. Slip ring induction motor
D. Any of the above

In a rotary converter I2R losses as compared to a D.C. generator of the same size will be___________?

A. Same
B. Less
C. Double
D. Three times

The potential drop in the arc, in a mercury arc rectifier, varies_____________?

A. 0.05 v to 0.2 v per cm length of the arc
B. 0.5 v to 1.5 v per cm length of the arc
C. 2 v to 3.5 v per cm length of the arc
D. None 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. it remains in liquid state at ordi¬nary temperature

Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of _____________?

A. 100 a at 100 v
B. 200 a at 200 v
C. 300 a at 300 v
D. 400 a at 400 v

The cathdde voltage drop, in a mercury arc rectifier, is due to_____________?

A. Expenditure of energy in ionization
B. Surface resistance
C. Expenditure of energy in overcoming the electrostatic field
D. Expenditure of energy in liberating electrons from the mercury

To produce cathode spot in a mercury arc rectifier______________?

A. Anode is heated
B. Tube is evacuated
C. An auxiliary electrode is used
D. Low mercury vapour pressures are used

The advantage of mercury arc rectifier is that________________?

A. it is light in weight and occupies small floor space
B. it has high efficiency
C. it has high overload capacity
D. it is comparatively nosieless