单项选择题
Which of the listed sections of an emergency switchboard is used to supply power for alarm signals under emergency conditions?（）
A.The generator and bus transfer section
B.The 450 volt, 60 cycle, 3 phase bus
C.The 120 volt, 3 phase, 60 cycle bus
D.The 24 volt DC bus
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When the current in a power transmission line is increased, the power loss （）
A.increases as the square of the current
B.decreases as the square root of the current
C.remains the same, as it is independent of current flow
D.increases in direct proportion as the current -
单项选择题
An operational amplifier, as used in todays consoles, may have a calculated gain of 5√This means that as the input changes by （）
A.1 volt, the output changes 5 volts
B.5 volts, the output changes 1 volt
C.5 volts, the output changes 10 volts
D.10 volts, the output changes 5 volts -
单项选择题
Why is it desirable to operate paralleled AC generators at the same power factor?（）
A.Circulating currents are kept to a minimum
B.Field excitation losses are kept to a minimum
C.Generator rotors will have a lesser tendency to hunt
D.Because a power factor increase will decrease kilowatt output
