如图所示电路,电源电压恒定不变.小灯泡L标有“3V 0.6W”字样,R为定值电阻.闭合S,断开S 1 ,小灯泡正

2025-04-29 20:55:07
推荐回答(1个)
回答1:

闭合S,断开S 1 时,为灯泡的基本电路,
∵小灯泡正常发光,
∴电源电压U=3V,P L =0.6W;
再闭合S 1 ,为并联电路,通过R的电流I R =0.1A,
R的阻值为R=
U
I R
=
3V
0.1A
=30Ω;
R的功率为P R =UI R =3V×0.1A=0.3W,
∴P L :P R =0.6W:0.3W=2:1.
故答案为:30,2:1.