单项选择题
A.one thousandth (10 to the -3rd power) B.one millionth ( 10 to the -6th power) C.one billionth ( 10 to the -9th power) D.one trillionth (10 to the -12th power)
A “dead front” switchboard is one （）.A.without switches...
单项选择题A “dead front” switchboard is one （）.
A.without switches on it B.with insulated switches and no exposed terminals C.without circuit breakers D.without safety hand nails nor rubber mats
The total resistance of a parallel circuit is always （）...
单项选择题The total resistance of a parallel circuit is always （）.
A.larger than the greatest branch resistance B.smaller than the lowest branch resistance C.equal to the sum of the individual branch resistances D.one-half the sum of the individual branch resistances
Reduced voltage applied to a motor during the starting ...
单项选择题Reduced voltage applied to a motor during the starting period will （）.
A.result in decreased acceleration time only B.lower the starting current and increase accelerating time C.cause a greater starting torque D.increase the starting current and pump capacity
