Applet shows electric field lines due to charges. Initially the two charges are equal and equal number of lines of force are drawn from them. The ratio of charges can be varied by increasing the charge on the right. The number of field lines from the charge on the right increase proportionately. The sign of the charge on the right can also be changed. Both equipotentials and field lines can be observed by checking the corresponding boxes. The adjacent equipotentials differ in potentials by equal amounts. It might help to uncheck the field lines checkbox while observing the equipotentials. When charges are equal left/right clicking increases/decreases the distance between the charges.