Question

Two coaxial rings, each of radius R, made of thin wire are separated by a small distance l (l < R) and carry the charges q and —q. Find the electric field potential and strength at the axis of the system as a function of the x coordinate (Fig. 3.6). Show in the same drawing the approximate plots of the functions obtained. Investigate these functions at | x | >> R.

Answer 1

The potential can be calculated by superposition. Choose the plane of the upper ring as x = l/2 and that of the lower ring as x = - l/2.

The plot is as given in the book.