单项选择题
A.replace all bearings regardless of length of service B.apply a heavy coat of oil to all mating surfaces C.clean any corroded surfaces and file all burrs smooth D.coat all parts with alemite grease
Ammeters and voltmeters used in sinusoidal AC power sys...
单项选择题Ammeters and voltmeters used in sinusoidal AC power systems indicate which of the following values of the waveforms measured?（）
A.Peak value B.Root-mean-square value C.Average value D.Maximum value
Fuses placed in series with a thermal trip-type circuit...
单项选择题Fuses placed in series with a thermal trip-type circuit breaker are used for （）.
A.time-delay protection B.short-circuit protection C.short duration surge protection D.sustained overload protection
The main difference between a motor control circuit con...
单项选择题The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains （）.
A.a magnetic operating coil B.normally open line contacts C.thermal-overload protection D.a momentary-contact start button
