电源开路时，其端电压和电动势的关系为相等。
参考答案：对
History is the best teacher. It _______records the development path of each country and foretells the future to us.
A．apparently
B．conventionally
C．faithfully
D．eventually
金属氧化锌避雷器运行中持续电流检测，每年雷雨季节来临前安排（）次。
A.1
B.2
C.3
D.4
