例如:∵∴
电源电压保持不变,R1+10Ω,R2=20Ω的小灯泡L正常发光时电压为6V.当S1、S2闭合时,灯L正常发光.求:①通过电阻R1的电流②当S1、S2断开时,灯L两端的电压.______R1________R2_____
S1||
|_____灯泡L___|_____S2____|
|____________||__________|
-+
______R1________R2_____
S1||
|_____灯泡L___|___S2_____||____________||__________|
-+