Practice Test: Question Set - 01
1. If cathode and anode connections in a mercury arc rectifier are inter changed
- (A) The rectifier will not operate
- (B) Internal losses will be reduced
- (C) Both ion and electron streams will move in the same
direction
- (D) The rectifier will operate at reduced efficiency
2. 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
3. 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
4. On which of the following factors the number of phases for which a rectifier should be designed depends?
- (A) The voltage regulation of the rectifier should be
low
- (B) In the output circuit there should be no harmonics
- (C) The power factor of the system should be high
- (D) All of the above
5. In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of
- (A) Shunt motor
- (B) Synchronous motor
- (C) Induction regulator
- (D) Synchronous generator
6. Selenium rectifier can be operated at temperatures as high as
- (A) 25°C
- (B) 40°C
- (C) 60°C
- (D) 75°C
7. A commutating rectifier consists of commutator driven by
- (A) An induction motor
- (B) A synchronous motor
- (C) A D.C. series motor
- (D) A D.C. shunt motor
8. The ignited or auxiliary anode in mercury arc rectifier is made of
- (A) Graphite
- (B) Boron carbide
- (C) Aluminium
- (D) Copper
9. The efficiency of the copper oxide rectifier seldom exceeds
- (A) 90 to 95%
- (B) 85 to 90%
- (C) 80 to 85%
- (D) 65 to 75%
10. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply?
- (A) Mechanical rectifiers
- (B) Copper oxide rectifiers
- (C) Selenium rectifiers
- (D) Electrolytic rectifiers
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