Question

Assume a uniformly charged ring of radius R and charge Q produces an electric field E(ring) at a point P on its axis, a distance x away from the center of the ring as in Figure. Now the same charge Q is spread uniformly over the circular area the ring encloses, forming a flat disk of charge with the same radius as in Figure b. How does the field E(disk) produce by the disk at P compared with the field produce by the ring at the same point?

1. E(disk)<E(ring)
2. E(disk)=E(ring)
3. E(disk)>E(ring)
4. impossible to determine