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單項(xiàng)選擇題

If a DC motor runs hot, the cause may be （）

A.high mica condition
B.low ambient temperature
C.clogged ventilation ducts
D.an open in the shunt field

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單項(xiàng)選擇題

The unit of electrical resistance is the （）

A.ampere
B.volt
C.watt
D.ohm

單項(xiàng)選擇題

Some large A-Cmotors are equipped with heatersThese could be （）
(1)resistance heaters bolted directly to the frame
(2)low voltage windings embedded in the motor windings

A.(1) only
B.(2) only
C.either (1) or (2)
D.neither (1) or (2)

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