单项选择题
A."slow" direction, just before the 12 o'clock position
B."fast" direction, just after the 12 o'clock position
C."fast" direction, just before the 12 o'clock position
D."slow" direction, just after the 12 o'clock position
单项选择题 AC voltmeters are generally calibrated to read the （）
单项选择题 You are attempting to parallel two AC generators, and the syncope pointer is revolving in the fast directionThis indicates that the frequency of the incoming machine is （）.
单项选择题 The voltage developed by an AC generator is controlled by varying the （）