单项选择题
If the resistance of a circuit is cut in half and the applied voltage is kept constant, the current flow will be （）.
A.doubled B.quadrupled C.unchanged D.cut in half
单项选择题 Equal power factors on paralleled AC generators are maintained by an automatic （）.
单项选择题 To equalize the power factor of two alternators operating in parallel, the （）
单项选择题 An advantage of DC motors over AC motors is that they （）
