例题 已知两带电细杆电荷线密度均为λ、长度为L,-|||-相距L,如图所示。 x'-|||-dx'-|||-求:两带电直杆间的电场力。-|||-0 k L 2L 3L x-|||-解:建立如图所示坐标系 x'-x-|||-在左、右两杆上分别选电荷元 =lambda dx-|||-.'=lambda dx'-|||-根据库仑定律 =dfrac (lambda dxlambda {x)^circ }(4pi {varepsilon )_(0)((x'-x))^2}-|||-3L-|||-F= '(int )_(0)^circ dfrac ({lambda )^2dx}(4pi {varepsilon )_(0)((x'-x))^2}=dfrac ({lambda )^2}(4pi {e)_(0)}ln dfrac (4)(3)