On an x'ox axis are placed: a point load q1 at point O, a point load q2 at the
Point A of abscissa x = a.

1 -Give the expression of the electrostatic force acting on a q3 charge placed on the axis at the
Point B x = a/2. We give q1 = 3q, q2 = -2q and q3 = q with q a positive charge.
Give the schema too
2 -Give the expression of the field and electrostatic potential at point B.