2.3.2 A sphere with volume charge

The same experience is repeated, but now the moving charge enters within a sphere with volume charge. The field outside the sphere is again the same as that of a point charge placed at the centre of the sphere, but the field inside the sphere does not vanish. Instead, the average field increases proportional to the distance from the centre.

Rotate with the xyZET keys to confirm that the charge distribution occupies the volume of the sphere. In the simulation, the sphere is modelled by means of point charges, thus causing strong fluctuations in the field when the test charge moves across the sphere. Nevertheless, it may be seen that the field cancels when the charge passes through the centre of the sphere.