开关S1闭合、S2断开,滑动变阻器的滑片P移到B端时,等效电路图如图①所示;
当开关S1断开、S2闭合时,等效电路图如图②所示;
当开关S1、S2都断开,滑动变阻器的滑片P在某点C时,等效电路图如图③所示;
(1)由图①②可知:
P2 |
P′2 |
| ||
|
| ||
|
U1 |
U2 |
I3(R1+RC) |
I3(RC +R2) |
R1+RC |
RC +R2 |
3 |
8 |
U |
RB+R2 |
U |
R1+R2 |
U |
R1+RC+R2 |
U |
R1+R2 |
U |
R1+RC+R2 |
U |
RB+R2 |
U |
R1+R2 |
PB |
PC |
| ||
|
(3)2×3 |
42×1 |
27 |
16 |