The charge on the metal sphere is chosen so that potential V of the surface of the
sphere with a radius of 1 unit is 10 V for a positively and -10 V for a negatively charged sphere.
(You can choose the distance units, for example cm. A sphere is chosen
because the potential of a point charge is not finite at the position of the
point charge.) The magnitude of the potential, |V|, decreases by 1 V
from one equipotential surface to the next. 10 surfaces are drawn.
The largest one has a radius of 10 units at a potential of magnitude 1 V. You
can cut through the surfaces at various distances from the center of the
charge and display the potential in the plane of the cut as a function of
the plane coordinates. In the potential versus plane coordinates plot
3D plot the magnitude of the potential is represented by the perpendicular
distance from the plane. The potential scale goes from 0 to 10 V.
You can rotate and zoom the equipotential surfaces plot and the potential versus plane coordinates plot separately by holding the left mouse button down over the chosen plot and then moving the mouse or the mouse wheel.