Question: Relative permeability of vacuum is__________?

• 1. 1
• 2. 1 H/m
• 3. 1/4JI
• 4. 4n x 10-‘ H/m

Question: Permeability in a magnetic circuit corresponds to________ in an electric circuit.

• 1. resistance
• 2. resistivity
• 3. conductivity
• 4. conductance

Question: The relative permeability of a ferromagnetic material is_____________?

• 1. less than one
• 2. more than one
• 3. more than 10
• 4. more than 100 or 1000

Question: The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following_____________?

• 1. anode drop and cathode drop
• 2. anode drop and arc drop
• 3. cathode drop and arc drop
• 4. anode drop, cathode drop and arc drop

Question: The ionization potential of mercury is approximately_____________?

• 1. 5.4 V
• 2. 8.4 V
• 3. 10.4 V
• 4. 16.4 V

Question: In a glass bulb mercury arc rectifier the maximum current rating is restricted to___________?

• 1. 2000 A
• 2. 1500 A
• 3. 1000 A
• 4. 500 A

Question: In a mercury arc rectifier characteristic blue luminosity is due to_____________?

• 1. colour of mercury
• 2. ionization
• 3. high temperature
• 4. electron streams

Question: When a rectifier is loaded which of the following voltage drops take place ?

• 1. Voltage drop in transformer reactance
• 2. Voltage drop in resistance of transformer and smoothing chokes
• 3. Arc voltage drop
• 4. All of the above

Question: Which of the following mercury arc rectifier will deliver least undulating current?

• 1. Six-phase
• 2. Three-phase
• 3. Two-phase
• 4. Single-phase

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

• 1. one-third of a cycle
• 2. one-fourth of a cycle
• 3. one-half a cycle
• 4. two-third of a cycle