R=
U额 |
I额 |
2.5V |
0.3A |
(2)回形针在最右端时,
U铅笔芯=U-U灯=3V-0.6V=2.4V,
铅笔芯接入电路的电阻:
R铅笔芯=
U铅笔芯 |
I |
2.4V |
0.1A |
(3)小灯泡正常发光时,U灯=2.5V,I′=0.3A,
铅笔芯两端的电压:
U铅笔芯′=U-U灯′=3V-2.5V=0.5V,
铅笔芯5min内消耗的电能:
W=U铅笔芯′I′t=0.5V×0.3A×5×60s=45J.
答:(1)小灯泡正常发光时的电阻为8.3Ω;
(2)回形针在最右端时,铅笔芯接入电路的电阻为24Ω;
(3)小灯泡正常发光时,铅笔芯5min内消耗的电能为45J.