a negatively charge particle is placed exactly midway between two fixed particles having equal positive charge.what will happen to the charge?

If +Q are the two positive charges placed ‘x’ distance apart and a negative charge –q is placed at midway between the positive charges, then the net Coulomb force experienced by the negative charge will be zero. The net electric field at the point of –q will also be zero. The potential at that point due to the positive charges will be a non-zero quantity (4kQ/x). The electric potential energy of –q at that point will be -4kQq/x. So, the negative charge will be in an unstable equilibrium.