A. lubricate the contacts
B. insulate the contacts from switch body
C. extinguish the arc
D. all of the above
E. none of the above
Related Mcqs:
- Oil switches are employed for_____________?
A. low currents circuits
B. low voltages circuits
C. high voltages and large currents circuits
D. all circuits - In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?
A. have low contact resistance
B. be clean and smooth
C. be of sufficient size and proper shape
D. have all above properties - The voltage appearing across the contacts after opening of the circuit breaker is called__________voltage
A. recovery
B. surge
C. operating
D. arc
E. none of the above - The arcing contacts in a circuit breaker are made of______________?
A. copper tungsten alloy
B. porcelain
C. electrolytic copper
D. aluminium alloy - Overheating of relay contacts or contact born out is due to_______________?
A. slow making and breaking of load circuit contacts
B. foreign matter on the contact surface
C. too low contact pressure
D. all of the above - Insulation resistance of high voltage circuit breakers is more than________________?
A. 1 mega ohms
B. 10 mega ohms
C. 100 mega ohms
D. 500 mega ohms - The current zero interruption, in oil and air blast circuit breakers, is achieved by_______________?
A. lengthening of the gap
B. cooling and blast effect
C. both A. and B
D. deionizing the oil with forced air
E. none of the above - The current zero interruption, in oil and air blast circuit breakers, is achieved by____________?
A. lengthening of the gap
B. cooling and blast effect
C. both (A) and (B)
D. deionizing the oil with forced air
E. none of the above - The under voltage relay can be used for______________?
A. generators
B. busbars
C. transformers
D. motors
E. all of the above - Over voltage protection is recommended for______________?
A. hydro-electric generators
B. steam turbine generators
C. gas turbine generators
D. all of the above
E. none of the above
