【单选题】电路如图所示。已知U2=20V,稳压管的 =9V,R=300Ω, =300Ω。若不慎将稳压管开路了,电路的输出电压 为 。
【单选题】There is no______on the bus, so we have to wait for another one.
【单选题】There is no ____ in the bus and we have to wait for another.
【简答题】Rewrite the following passage, giving the sentences some variety in length and structure I got up a little later than usual on Sunday morning. I washed and had a quick breakfast. Then I started going ...
【单选题】若电路如图示,已知U 2 =20V,测得输出电压为28 V,可能的原因是: ______。
【单选题】若电路如图示,已知U 2 =20V,测得输出电压为9V,可能的原因是: ______。