The applications of selenium rectifiers are usually limited to potential of_____________?

Related Mcqs:

1. In selenium rectifiers efficiencies ranging from _______ to _______ percent are attainable?

   A. 25, 35
   B. 40, 50
   C. 60, 70
   D. 75, 85

2. 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

3. 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

4. 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
   E. 500 A at 500 V

5. Selenium rectifier can be operated at temperatures as high as____________?

   A. 25°C
   B. 40°C
   C. 60°C
   D. 75°C

6. 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

7. Which of the following rectifiers have been used extensively in supplying direct current for electroplating ?

   A. Copper oxide rectifiers
   B. Selenium rectifiers
   C. Mercury arc rectifiers
   D. Mechanical rectifiers
   E. None of the above

8. 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

9. 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

10. 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