單項(xiàng)選擇題Inductance is the property of an electric circuit that （）

A.opposes any change in the applied voltage
B.opposes any change in the current flow through the circuit
C.aids any changes in the applied voltage
D.aids any changes in the current through the circuit


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1.單項(xiàng)選擇題The operator of electrical motors should keep a constant check on the loads they carry because （）

A.low loads necessitate frequent insulation cleaning
B.exceeding nameplate values shortens useful life
C.energy is wasted if full loading is not utilized
D.power factor correction methods are load dependent

2.單項(xiàng)選擇題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

3.單項(xiàng)選擇題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

4.單項(xiàng)選擇題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

5.單項(xiàng)選擇題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