When the program starts, it automatically sets up a set of three charges. Clicking Select draws an equipotential through the point. Move the mouse to a few points and Click Select. You quickly build up a representative set of equipotentials.
Click Menu and choose Electric field. Clicking Select at a point now draws the electric field line through the point. Do this for a few points. Notice that the field lines are always at right angles to the equipotentials.
Heading: Special cases.
The most important special case is a single point charge. Remove charges until only one charge of 200 micro Coulombs remains. Move it into the centre of the square and draw equipotentials at approximately 0.5, 1.0, 1.5 and 2 Volts respectively.
Notice that the circles of equal voltage get closer together as you move nearer to the charge. The running commentary from the mouse also shows this. Draw a few electric field lines. They all point directly away from the charge.
Heading: Special case: the dipole.
Choose the Dipole option from the Special cases sub-menu, and draw some equipotentials and field lines.
