The arc voltage produced in A.C. circuit breaker is always_____________?

A. in phase with the arc current
B. lagging the arc current by 90″
C. leading the arc current by 90°
D. none of the above

Which of the following medium is employed for extinction of arc in air circuit breaker?
A. Water B. Oil C. Air D. SF6...
Arc in a circuit breaker is interrupted at___________?
A. zero current B. maximum current C. minimum voltage D. maximum voltage...
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...
With which of the following, a circuit breaker must be equipped for remote operation ?
A. Inverse time trip B. Time-delay trip C. Shunt trip D. None of the above E. All of the above...
Thermal circuit breaker has____________?
A. delayed trip action B. instantaneous trip action C. both of the above D. none of the above...
Magnetic circuit breaker has ___________ trip action
A. delayed B. instantaneous C. both of the above D. 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...
Air blast circuit breaker is used for_____________?
A. over currents B. short duty C. intermittant duty D. repeated duty...
In a circuit breaker the basic problem is to________________?
A. maintain the arc B. extinguish the arc C. transmit large power D. emit the ionizing electrons...
Ionization in circuit breaker is facilitated by___________?
A. high temperature B. increase of mean free path C. increasing field strength D. all of the above...