Circuit breakers are essentially____________? A. current carrying contacts called electrodes B. arc extinguishers C. circuits to break the system D. transformers to isolate the two systems E. any of the above
Circuit breakers are essentially______________? A. current carrying contacts called electrodes B. arc extinguishers C. circuits to break the system D. transformers to isolate the two systems E. any of the above
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 shapeD. have all above properties
Thermal overload relays are used to protect the motor against over current due to____________? A. short-circuitsB. heavy loads C. grounds D. all of the above
Overload relays are of_______________type A. induction B. solid state C. thermal D. electromagneticE. all above
A thermal protection switch can protect against_____________? A. short-circuit B. temperatureC. overload D. over voltage
SF6 gas______________? A. is yellow in colour B. is lighter than airC. is nontoxic D. has pungent small E. none of the above
Which of the following medium is employed for extinction of arc in air circuit breaker? A. Water B. OilC. Air D. SF6
On which of the following routine tests are conducted ? A. Oil circuit breakers B. Air blast circuit breakers C. Minimum oil circuit breakersD. 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