Question: Circuit breakers usually operate under______________?

• 1. transient state of short-circuit current
• 2. sub-transient state of short-circuit current
• 3. steady state of short-circuit current
• 4. after DC component has ceased

Question: D.C. shunt relays are made of_____________?

• 1. few turns of thin wire
• 2. few turns of thick wire
• 3. many turns of thin wire
• 4. many turns of thick wire

Question: Circuit breakers are essentially____________?

• 1. current carrying contacts called electrodes
• 2. arc extinguishers
• 3. circuits to break the system
• 4. transformers to isolate the two systems

Question: Circuit breakers are essentially______________?

• 1. current carrying contacts called electrodes
• 2. arc extinguishers
• 3. circuits to break the system
• 4. transformers to isolate the two systems

Question: In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?

• 1. have low contact resistance
• 2. be clean and smooth
• 3. be of sufficient size and proper shape
• 4. have all above properties

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