+q的位置0,+=)= q的位置(00,-)=E 线性叠加原理 (F)=V+(F)+V(F) 4ms0|-F|4xE0|产-F F-F厂=(-F)(F-F 2F]2≈(r2-2F,元) 2 F·F1F·F (1 (1+-2) 同理|- 48 qF·(-F)1F 4 4丌 2.电四极子 定义 q(0,0,)=F1-q(0,0,0) a (0,0,-()=F2 (0,0,0)=F q+q 的位置 (0,0, ) 2 r + = + l r −q 的位置 (0,0, ) 2 r − = − l r 线性叠加原理 0 0 1 1 () () () 4 | | 4 | | q q Vr V r V r πε rr rr πε + − + − − =+= + − − r rr r r r r 1 1 2 | | rr rr rr (( ) ( ))− − − = − ⋅− + ++ rr rr rr 1 1 2 2 2 2 2 [ 2] (2 r r rr r rr ) − − = +−⋅ ≈ −⋅ + + + r r r r 1 2 2 2 1 11 2 (1 ) (1 ) rr rr rr r r r r rr − 3 + + + ⋅ ⋅ ⋅ = − ≈ + =+ rr rr rr 同理 1 3 1 | | r r r r r r − r ⋅ − − ≈+ − r r r 3 3 0 1 1 () [ ] 4 q rr rr V r πε rr rr + − ⋅ ⋅ = + −− r r r r r 3 33 0 00 ( ) 1 1 ~ 4 44 q r rr r q r rr ρ πε πε πε + − ⋅ − ⋅ ⋅ = == 2 r 1 r rr r r r r r l 2．电四极子 定义： 1 q r (0,0, ) + = + r l 1 q r (0,0,0) − = − r 2 q r (0,0, ) + − = + r l 2 q r (0,0,0) − = − r +q -q p -q +q p