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

• 1. 25, 35
• 2. 40, 50
• 3. 60, 70
• 4. 75, 85

Question: A commutating rectifier consists of commutator driven by___________?

• 1. an induction motor
• 2. a synchronous motor
• 3. a DC series motor
• 4. a DC shunt motor

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

• 1. copper
• 2. aluminium
• 3. silver
• 4. graphite

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

• 1. Copper oxide rectifiers
• 2. Selenium rectifiers
• 3. Mercury arc rectifiers
• 4. Mechanical rectifiers

Question: Which of the following is the loss within the mercury arc rectifier chamber ?

• 1. Voltage drop in arc
• 2. Voltage drop at the anode
• 3. Voltage drop at the cathode
• 4. All of the above

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

• 1. Mechanical rectifiers
• 2. Copper oxide rectifiers
• 3. Selenium rectifiers
• 4. Electrolytic rectifiers

Question: The efficiency of an electrolytic rectifier is nearly____________?

• 1. 80%
• 2. 70%
• 3. 60%
• 4. 40%

Question: The ignited or auxiliary anode in mercury arc rectifier is made of____________?

• 1. graphite
• 2. boron carbide
• 3. aluminium
• 4. copper

Question: he retentivity (a property) of material is useful for the construction of_______________?

• 1. permanent magnets
• 2. transformers
• 3. non-magnetic substances
• 4. electromagnets

Question: A permanent magnet______________?

• 1. attracts some substances and repels others
• 2. attracts all paramagnetic substances and repels others
• 3. attracts only ferromagnetic substances
• 4. attracts ferromagnetic substances and repels all others