问题
选择题
下列四只灯泡正常发光时,灯丝中电流最小的是( )
A.“220V 25W”
B.“220V 60W”
C.“36V 40W”
D.“110V 100W”
答案
∵P=UI,
∴灯泡正常发光时的电流:
I1=
=P1 U1
≈0.11A,25W 220V
I2=
=P2 U2
≈0.27A,60W 220V
I3=
=P3 U3
≈1.1A,40W 36V
I4=
=P4 U4
≈0.91A,100W 110V
则灯“220V 25W”正常发光时电流最小;
故选A.