When the separation between two charges is increased, the electric potential energy of the charges:

As per this diagram, a point charge \(+q\) is placed at the origin \(O.\) Work done in taking another point charge \(-Q\) from the point \(A,\) coordinates \((0,a),\) to another point \(B,\) coordinates \((a,0),\) along the straight path \(AB\) is:

A positively charged light particle of charge \(q\) and mass \(m\) approaches another heavy particle of positive charge \(Q,\) coming towards it with an initial speed \(u,\) when it is far away.
                 
The distance of the closest approach is given by:

1. \(\frac{q Q}{4 \pi \varepsilon_{0} m u^{2}}\)

2. \(\frac{q Q}{\pi \varepsilon_{0} m u^{2}}\)

3. \(\frac{q Q}{2 \pi \varepsilon_{0} m u^{2}}\)

4. \(\frac{4 \pi \varepsilon_{0} m u^{2}}{q Q}\)