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单选题
Possible phase relationships between voltage and current in an alternating current circuit include which of the following conditions?（）
A
Current and voltage may be in phase
B
Current may lead the voltage
C
Current may lag the voltage
D
All of the above
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efficiencyC
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考题
单选题With a （） load the voltage and current are in phase.A
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using higher current and lower voltage increasing theC
number of thermal relays in the circuitD
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minimumB
maximumC
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cosineC
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result in decreased acceleration time onlyB
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may be neglectedC
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is considerable
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the recommended current and voltage ratingB
higher current and voltage ratingC
higher current and lower voltage ratingD
lower current and higher voltage rating
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generate its own electrical powerB
transform electrical energy into mechanical energyC
increase or decrease circuit voltage as requiredD
convert AC current to DC current
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