Given are four arrangements of three fixed electric charges.

Given are four arrangements of three fixed electric charges. In each arrangement, a point labelled `P` is also identified- test charge, `+q`, is placed at point `P`. All of the charges are of same magnitude `Q`, but they can be either positive of negative as indicated. The charges and point `P` all lie on a straight line. The distances between adjacent items, either between two charges or between a charge and point `P`, all are the same.