单项选择题
A.waterproof B.drip proof C.spray tight D.spray proof
Universal motors will operate on AC or DC current, and ...
单项选择题Universal motors will operate on AC or DC current, and are generally found in （）
A.portable tools B.large pump motors C.turbo electric main motors D.forced draft fans
An operational amplifier, as used in todays consoles, h...
单项选择题An operational amplifier, as used in todays consoles, has a calculated gain of 5This means that when the input changes （）
A.5 volts, the output changes 10 volts B.10 volts, the output changes 5 volts C.2 volts, the output changes 10 volts D.10 volts, the output changes 2 volts
Electrical failures in motors are caused by the breakdo...
单项选择题Electrical failures in motors are caused by the breakdown of insulation, which may be caused by （）
A.penetration of moisture B.accumulation of dirt C.overheating D.All of the above
