A. anode is heated
B. tube is evacuated
C. an auxiliary electrode is used
D. low mercury vapour pressures are used
Related Mcqs:
- 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______________?
A. maximum grid voltage
B. critical grid voltage
C. any of the above
D. none of the above - In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.
A. accelerates
B. decelerates
C. any of the above
D. none of the above - In a mercury arc rectifier________ flow from anode to cathode
A. ions
B. electrons
C. ions and electrons
D. any of the above - The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following_____________?
A. anode drop and cathode drop
B. anode drop and arc drop
C. cathode drop and arc drop
D. anode drop, cathode drop and arc drop - If cathode and anode connections in a mercury arc rectifier are inter changed_____________?
A. the rectifier will not operate
B. internal losses will be reduced
C. both ion and electron streams will move in the same direction
D. the rectifier will operate at reduced efficiency - 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
E. all of the above - 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 - The ignited or auxiliary anode in mercury arc rectifier is made of____________?
A. graphite
B. boron carbide
C. aluminium
D. copper - In a three-phase mercury arc rectifiers each anode conducts for____________?
A. one-third of a cycle
B. one-fourth of a cycle
C. one-half a cycle
D. two-third of a cycle - The internal efficiency of a mercury arc rectifier depends on___________?
A. voltage only
B. current only
C. voltage and current
D. r.m.s. value of current
E. none of the above
