A. have low contact resistance
B. be clean and smooth
C. be of sufficient size and proper shape
D. have all above properties
Related Mcqs:
- 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 - Admittance relay is __________ relay?
A. impedance
B. directional
C. non-directional
D. none of the above - 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 contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to______________?
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 - The under voltage relay can be used for______________?
A. generators
B. busbars
C. transformers
D. motors
E. all 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 - The relay operating speed depends upon_________________?
A. the spring tension
B. the rate of flux built up
C. armature core air gap
D. all of the above - Interruption of large currents by relay requires______________?
A. arc suppressing blow out coils
B. wide separation of the opened contacts
C. high speed opening of contacts
D. all of the above - If the fault occurs near the impedance relay, the VII ratio will be____________?
A. constant for all distances
B. lower than that of if fault occurs away from the relay
C. higher than that of if fault occurs away from the relay
D. none of the above - The torque produced in induction type relay (shaded pole structure) is_____________?
A. inversely proportional to the current
B. inversely proportional to the square of the current
C. proportional to the current
D. proportional to square of the current
