Question

一道计算题~有图如图的电路中,电源电压未12伏,且保持不变,当电键S闭合时,电流表A的示数未0.2安,电压表V的示数为8

Answer 1

1.I=U/R

R=U/I

=8/0.2

=40欧

2.I=U/R

=12/40

=0.3安

3.P=UI

=12*0.3

=3.6瓦