A point charge \(q\) is rotated along a circle in the electric field generated by another point charge \(Q\). The work done by the electric field on the rotating charge in one complete revolution is:
1. zero.
2. positive.
3. negative.
4. zero if the charge \(Q\) is at the centre and non-zero otherwise.

The energy density in the electric field created by a point charge falls off with the distance from the point charge as:
1. \(\dfrac{1}{r}\)

2. \(\dfrac{1}{r^2}\)

3. \(\dfrac{1}{r^3}\)

4. \(\dfrac{1}{r^4}\)