Electric Field of Line Charge

The electric field of a line of charge can be found by superposing the point charge fields of infinitesmal charge elements. The radial part of the field from a charge element is given by

The integral required to obtain the field expression is

Electric Field: Ring of Charge

The electric field of a ring of charge on the axis of the ring can be found by superposing the point charge fields of infinitesmal charge elements. The ring field can then be used as an element to calculate the electric field of a charged disc.

The electric fields in the xy plane cancel by symmetry, and the z-components from charge elements can be simply added. xy平面内的电场因对称性而相互抵消，而由电荷元产生的z方向分量可以简单相加。 If the charge is characterized by an area density and the ring by an incremental width dR' , then: 如果电荷由面积密度表示，而环则由微小宽度dR'表示，那么： This is a suitable element for the calculation of the electric field of a charged disc. 这适用于计算带电圆盘的电场。

Electric Field:Disc of Charge