单选题A transformer in an electric circuit serves to （）Agenerate its own electrical powerBtransform electrical energy into mechanical energyCincrease or decrease circuit voltage as requiredDconvert AC current to DC current
单选题
A transformer in an electric circuit serves to （）
A
generate its own electrical power
B
transform electrical energy into mechanical energy
C
increase or decrease circuit voltage as required
D
convert AC current to DC current
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