Two classic examples are considered in this Demonstration. A point charge located at near an infinite grounded plane conductor at has the same potential distribution as a pair of charges and symmetrically placed with respect to the plane. The potential is then given by . The labeled equipotentials in the contour plot can be multiplied by to give their actual values. A point charge at either inside or outside a grounded spherical conductor of radius , centered at the origin, can be solved by placing an image charge -- at .

You can drag the point charge , a locator. A checkbox enables you to see the image charge . It will go off-scale if the locator is too close to the center of the sphere, but it still contributes to the potential.