单项选择题
A.relative speed of the rotor poles B.number of turns of wire in the armature coil C.strength of the magnets used D.output voltage
The greatest detrimental effect on idle electrical equi...
单项选择题The greatest detrimental effect on idle electrical equipment, such as cargo pump motors, is the（）.
A.loss of residual magnetism B.absorption of moisture in the insulation C.insulation varnish flaking D.dirt collecting on the windings
The Wheat-stone bridge is a precision measuring instrum...
单项选择题The Wheat-stone bridge is a precision measuring instrument utilizing the principle of changes in（）.
A.inductance B.capacitance C.resistance D.amperage
Which of the motors for the devices listed below is fit...
单项选择题Which of the motors for the devices listed below is fitted with an instantaneous overload relay?（）
A.Fan B.Pump C.Winch D.Machine tool
