A. delayed trip action
B. instantaneous trip action
C. both of the above
D. none of the above
A. Photoelectric effect
B. Electrostatic effect
C. Heating effect
D. Magnetic effect
A. to operate the relay of circuit breaker
B. as a substitute for circuit breaker
C. always independent of the position of circuit breaker
D. generally on both sides of a circuit breaker
A. 20 A
B. 50 A
C. 100 A
D. 200 A
A. low currents circuits
B. low voltages circuits
C. high voltages and large currents circuits
D. all circuits
A. Induction type
B. Reactance
C. Impedance
D. None of the above
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