1. Which of the following are the applications of D.C. system ?

Battery charging work

Arc welding

Electrolytic and electro-chemical processes

All of the above

Answer: All of the above


2. Which of the following methods may be used to convert AC. system to D.C. ?


Motor converters

Motor-generator sets

All of the above

Answer: All of the above


3. 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 ?



any of the above

none of the above

Answer: accelerates


4. Ageing of a selenium rectifier may change the output voltage by ?

5 to 10 per cent

15 to 20 per cent

25 to 30 per cent

none of the above

Answer: 5 to 10 per cent


5. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC supply ?

Mechanical rectifiers

Copper oxide rectifiers

Selenium rectifiers

Electrolytic rectifiers

Answer: Electrolytic rectifiers


6. The ignited or auxiliary anode in mercury arc rectifier is made of ?


boron carbide



Answer: boron carbide


7. The metal rectifiers, as compared to mercury arc rectifiers ?

operate on low temperatures

can operate on high voltages

can operate on heavy loads

give poor regulation

Answer: operate on low temperatures


8. The applications of selenium rectifiers are usually limited to potential of ?

10 V

30 V

60 V

100 V

Answer: 100 V


9. Which of the following statement is incorrect ?

Copper oxide rectifier is a linear device

Copper oxide rectifier is not a perfect rectifier

Copper oxide rectifier has a low efficiency

Copper oxide rectifier finds use in control circuits

Answer: Copper oxide rectifier is a linear device


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

The voltage regulation of the rectifier should be low

ln the output circuit there should be no harmonics

The power factor of the system should be high

all of the above

Answer: all of the above