(2008?昌平区二模)如图所示的电路中,R为滑动变阻器,R1、R2为定值电阻,且R1>R2,E为电压恒定的电源,当滑动变阻器的滑片滑动时,通过R、R1、R2的电流将发生变化,电流变化值分别为△I、△I1、△I2表示,则( )A.当滑动片向右滑动时,有△I1<△I<△I2B.当滑动片向左滑动时,有△I<△I1<△I2C.无论滑动片向左还是向右滑动,总有△I=△I1=△I2D.无论滑动片向左还是向右滑动,总有△I>△I2>△I1
RR总 |
R+1 |
3R+2 |
R+1 |
3R+2 |
R |
R+1 |
R |
3R+2 |
U并 |
R |
1 |
3R+2 |
U并 |
R′+1 |
3R′+2 |
R′?R |
(3R+2)×(3R′+2) |
1 |
3R+2 |
1 |
3R′+2 |
3(R′?R) |
(3R+2)×(3R′+2) |
R |
3R+2 |
R′ |
3R′+2 |
2(R′?R) |
(3R+2)×(3R′+2) |