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

• 1. shunt motor
• 2. synchronous motor
• 3. induction regulator
• 4. synchronous generator

Question: 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______________?

• 1. maximum grid voltage
• 2. critical grid voltage
• 3. any of the above
• 4. none of the above

Question: Which of the following statement is incorrect ?

• 1. Copper oxide rectifier is a linear device
• 2. Copper oxide rectifier is not a perfect rectifier
• 3. Copper oxide rectifier has a low efficiency
• 4. Copper oxide rectifier finds use in control circuits

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

• 1. magnitude
• 2. polarity
• 3. phase
• 4. any of the above

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

• 1. They are mechanically strong
• 2. They do not require any voltage for filament heating
• 3. Both (A) and (B)
• 4. None of the above

Question: Copper oxide rectifier is usually designed not to operate above___________?

• 1. 10°C
• 2. 20°C
• 3. 30°C
• 4. 45°C

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

• 1. 5 to 10 per cent
• 2. 15 to 20 per cent
• 3. 25 to 30 per cent
• 4. none of the above

Question: The efficiency of the copper oxide rectifier seldom exceeds____________?

• 1. 90 to 95%
• 2. 85 to 90%
• 3. 80 to 85%
• 4. 65 to 75%

Question: Selenium rectifier can be operated at temperatures as high as____________?

• 1. 25°C
• 2. 40°C
• 3. 60°C
• 4. 75°C

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

• 1. 10 V
• 2. 30 V
• 3. 60 V
• 4. 100 V