Electrical Engineering Mcqs Practice Test

Question 1

In a three-phase mercury arc rectifiers each anode conducts for____________?

Accepted Answer

A. one-third of a cycle

Question 2

In a mercury arc rectifier________ flow from anode to cathode

Accepted Answer

A. ions

Question 3

A mercury arc rectifier possesses __________ regulation characteristics

Accepted Answer

D. none of the above

Question 4

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.

Accepted Answer

A. accelerates

Question 5

On which of the following factors the number of phases for which a rectifier should be designed depend ?

Accepted Answer

E. all of the above

Question 6

It is the_________of the transformer on which the magnitude of angle of overlap depends?

Accepted Answer

C. leakage reactance

Question 7

In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of______________?

Accepted Answer

C. induction regulator

Question 8

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______________?

Accepted Answer

B. critical grid voltage

Question 9

Which of the following statement is incorrect ?

Accepted Answer

A. Copper oxide rectifier is a linear device

Question 10

In phase-shift control method the control is carried out by varying the of grid voltage

Accepted Answer

C. phase

Question 11

The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?

Accepted Answer

C. Both (A) and (B)

Question 12

Copper oxide rectifier is usually designed not to operate above___________?

Accepted Answer

D. 45°C

Question 13

Ageing of a selenium rectifier may change the output voltage by__________?

Accepted Answer

A. 5 to 10 per cent

Question 14

The efficiency of the copper oxide rectifier seldom exceeds____________?

Accepted Answer

D. 65 to 75%

Question 15

Selenium rectifier can be operated at temperatures as high as____________?

Accepted Answer

D. 75°C

Question 16

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

Accepted Answer

D. 100 V

Question 17

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

Accepted Answer

D. 75, 85

Question 18

A commutating rectifier consists of commutator driven by___________?

Accepted Answer

B. a synchronous motor

Question 19

In a mercury arc rectifier, the anode is usually made of_____________?

Accepted Answer

D. graphite

Question 20

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

Accepted Answer

B. Selenium rectifiers