Electric Potential Energy

When a proton approaches another fixed proton, what happens to : (a) the kinetic energy of the approaching proton (b) the electric potential energy potential energy of the system and (c ) the total energy of the system ?

A point charge q_1 is held stationary at the origin. A second charge q_2 is placed at a point a, and the electric potential energy of the pair of charges is -6.4 xx 10^-8 J . When the second charge is moved to point b, the electric force on the charge does 4.2 xx 10^-8 J of work. What is the electric potential energy of the pair of charges when the second charge is at point b?

Is it possible to have an arrangement of two point charges separated by finite distances such that the electric potential energy of the arrangement is the same as if the two charges were infinitely far apart? What if there are three charges?

Three point charges are arranged at the vertices of an equilateral triangle ABC of side l. Charges at A, B and C are +q, +4q and -6q, respectively. (i) Calculate electric potential energy of this system. (ii) Charge at A is moved to the midpoint of AB, charge at B is moved to midpoint of BC and charge at C is moved to midpoint of CA. Calculate electric potential energy of this system now. (iii) What work is needed to shift the charges to new locations as described in part (ii)?

A uniform electric field E_0 is directed along positive y-driection. Find the change in electric potential energy of a positive test charge q_0 when it is displaced in this field from y_i=a to y_f=2a along the y-axis.

If the p.d. across the ends of a capacitor 4muF is 1.0 kilovolt. Then its electrical potential energy will be

Two point charges 2q and 8q are placed at a distance r apart. Where should a third charge -q be placed between them so that the electrical potential energy of the system is a minimum