Related Questions

The applications of selenium rectifiers are usually limited to potential of
A 10 V
B 30 V
C 60 V
D 100 V
E 200 V
The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?
A They are mechanically strong
B They do not require any voltage for filament heating
C Both (A) and (B)
D None of the above
The metal rectifiers, as compared to mercury arc rectifiers
A operate on low temperatures
B can operate on high voltages
C can operate on heavy loads
D give poor regulation
E none of the above
In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid.
A Equal to
B More than
C Less than
D Either more or less than (depending upon the fluid)
A recent study shows that selenium , a mineral →bfound in in seafood, →cis linked to →dreducethe human cancer risk
A a
B b
C c
D d
Selenium is _____ semiconductor.
A Extrnisic
B Intmisic
C N-type
D P-type
Ageing of a selenium rectifier may change the output voltage by
A 5 to 10 per cent
B 15 to 20 per cent
C 25 to 30 per cent
D none of the above
Selenium rectifier can be operated at temperatures as high as
A 25°C
B 40°C
C 60°C
D 75°C
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
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

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