如图所示,灯L标有“6V 3W”字样,电源电压为9V且保持不变.闭合开关S,灯L正常发光,求: (1)电阻R的阻值; (2)灯泡正常发光时电阻R消耗的功率.

问题描述:

如图所示,灯L标有“6V 3W”字样,电源电压为9V且保持不变.闭合开关S,灯L正常发光,求:

(1)电阻R的阻值;
(2)灯泡正常发光时电阻R消耗的功率.

(1)I=

PL
UL
=
3W
6V
=0.5A,
UR=U-UL=9V-6V=3V,
R=
UR
I
=
3V
0.5A
=6Ω.
(2)PR=URI=3V×0.5A=1.5W.
答:(1)电阻R的阻值是6Ω.
(2)灯泡正常发光时电阻R消耗的功率1.5W.