单项选择题
A.adding rubber insulation conductors to the circuit
B.using higher current and lower voltage increasing the
C.number of thermal relays in the circuit
D.using higher voltage and lower current
单项选择题 Which of the following components are used to convert alternating current produced in the generator windings to direct current?（）
单项选择题 In a series circuit, which value will remain unchanged at all places in the circuit?（）
单项选择题 Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.