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.
答
(1)I=
=PL UL
=0.5A,3W 6V
UR=U-UL=9V-6V=3V,
R=
=UR I
=6Ω.3V 0.5A
(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.