G=G1+G2+G3+.+gn r RI R2 R3 R 两个电阻并联: 尺2 l1 尺1+R R R 12= 尺1+Rn n R R R R R G G G G G 1 1 1 1 1 1 2 3 1 2 3 = + + ++ = + + ++ 两个电阻并联： u i i1 i2 R1 R2 i R R R i i R R R i 1 2 1 2 1 2 2 1 + = + =