Question: Thermal overload relays are used to protect the motor against over current due to____________?

• 1. short-circuits
• 2. heavy loads
• 3. grounds
• 4. all of the above

Question: Overload relays are of_______________type.

• 1. induction
• 2. solid state
• 3. thermal
• 4. all above

Question: A thermal protection switch can protect against_____________?

• 1. short-circuit
• 2. temperature
• 3. overload
• 4. over voltage

Question: SF6 gas______________?

• 1. is yellow in colour
• 2. is lighter than air
• 3. is nontoxic
• 4. has pungent small

Question: Which of the following medium is employed for extinction of arc in air circuit breaker?

• 1. Water
• 2. Oil
• 3. Air
• 4. SF6

Question: On which of the following routine tests are conducted ?

• 1. Oil circuit breakers
• 2. Air blast circuit breakers
• 3. Minimum oil circuit breakers
• 4. All of the above

Question: The arcing contacts in a circuit breaker are made of______________?

• 1. copper tungsten alloy
• 2. porcelain
• 3. electrolytic copper
• 4. aluminium alloy

Question: Arc in a circuit behaves as_______________?

• 1. a capackive reactance
• 2. an inductive reactance
• 3. a resistance increasing with voltage rise across the arc
• 4. a resistance decreasing with voltage rise across the arc

Question: Fault diverters are basically____________?

• 1. fuses
• 2. relays
• 3. fast switches
• 4. circuit breakers

Question: Magnetic circuit breaker has ___________ trip action.

• 1. delayed
• 2. instantaneous
• 3. both of the above
• 4. none of the above