设两电荷连线中点为原点,两电荷距离2L,正电荷在x轴正半轴上：连线上电势U=kQ[(abs(x-L))^(-1)-(abs(x+L))^(-1)]；场强为E=kQ[(abs(x-L))^(-3)*(x-L)-(abs(x+L))^(-3)*(x+L)]；中垂线上电势U'=0；场强E'=2kQ(y^2+L^2)^(-1.5)*L