單項(xiàng)選擇題Before doing maintenance on electrical equipment, you should ().

A.turn off power first
B.turn on power first
C.with a test pen in hand
D.tell C/E


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1.單項(xiàng)選擇題While the parallel operation, () must be used.

A.ammeter
B.voltmeter
C.synchroscope
D.A+B+C

2.單項(xiàng)選擇題When the bearing becomes dry from lack of oil, the motor shaft may heat to ()an extent () it welds itself to the bearing.

A.either;or
B.neither;nor
C.such;that
D.so;that

4.單項(xiàng)選擇題When a sudden increase in steam demand comes to normal, the drum pressure will and water level in the drum will().

A.rise, rise also
B.rise, drop
C.drop, rise
D.drop, drop also

5.單項(xiàng)選擇題If a hydraulic pump is overheating, the cause may be ().

A.excessive internal leakage in the pump
B.low discharge pressure and fluid flow
C.excessive fluid level in the hydraulic reservoir
D.operation of the pump at 100% efficiency