单项选择题
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
A three-phase alternator operates at 450 volts with a p...
单项选择题A three-phase alternator operates at 450 volts with a power factor of 0~8.If the ammeter indicates 250 amperes, what should be the KW meter reading （）.
A.90~0 kw B.127~27 kw C.155~70 kw D.194~85 kw
Sparking at the brushes of a running motor could be an ...
单项选择题Sparking at the brushes of a running motor could be an indication of （）.
A.normal operation B.a dirty commutator C.increased brush capacity D.water vapor absorption
