The diagram shows two points P and Q positioned $90^\circ$ apart on a circle with radius $r$. A positive point charge at the centre of the circle produces an electric field of magnitude $E$ at both P and Q. Which expression gives the work done when a unit positive charge is moved from P to Q?
- A0
- B$E \times r$
- C$E \times \left(\frac{\pi r}{2}\right)$
- D$E \times (\pi r)$