Example: A disc of radius R has a uniform charge per unit area ƒã. Calculate the electric field at a point P along the central axis of the disc at a distance x0 from its center.

Question

Example: A disc of radius R has a uniform charge per unit area ƒã.  Calculate the electric field at a point P along the central axis of the disc at a distance x0 from its center.

drwls · Answer

You need to perform a Coulomb's-Law integration of the contribution of each surface area element of charge to the axial field. As a result of symmetry, the field at xo is directed along the central axis of symmetry. The integration over area can be performed as a one-dimensional integration over rings of radius r and width dr, with r running from 0 to R.