由名牌信息可知两灯泡的额定电压与额定功率,两灯泡的额定电流及灯泡电阻分别为:
额定电流I 1=
P 1
U 1 =
3W
6V =0.5A,灯泡电阻R 1=
U 1
I 1 =
6V
0.5A =12Ω;
额定电流I 2=
P 2
U 2 =
6W
6V =1A,灯泡电阻R 2=
U 2
I 2 =
6V
1A =6Ω;
两灯泡串联,使其中一个灯泡能正常发光,电路电流应为I=I 1=0.5A,
则加在串联电路两端的电压U=I 1(R 1+R 2)=0.5A×(12Ω+6Ω)=9V.
故选A.
由名牌信息可知两灯泡的额定电压与额定功率,两灯泡的额定电流及灯泡电阻分别为:
额定电流I 1=
P 1
U 1 =
3W
6V =0.5A,灯泡电阻R 1=
U 1
I 1 =
6V
0.5A =12Ω;
额定电流I 2=
P 2
U 2 =
6W
6V =1A,灯泡电阻R 2=
U 2
I 2 =
6V
1A =6Ω;
两灯泡串联,使其中一个灯泡能正常发光,电路电流应为I=I 1=0.5A,
则加在串联电路两端的电压U=I 1(R 1+R 2)=0.5A×(12Ω+6Ω)=9V.
故选A.