L1的额定电流:I1=
=P1 U1
=0.5A,R1=3W 6V
=
U
P1
=12Ω;(6V)2 3W
L2的额定电流:I2=
=P2 U2
=1.5A,R2=9W 6V
=
U
P2
=4Ω;(6V)2 9W
比较可知:I1<I2,
∵在串联电路中,电流处处相等,
∴此时电路中的电流应是I1,即L1正常发光,否则,会损坏L1,
电路两端的总电压为:U=I1(R1+R2)=0.5A×(12Ω+4Ω)=8V.
答:应该让灯L1正常发光,此时加在电路两端的总电压是8V.