An electron is constrained to the central axis of a ring of charge 1 coulomb and of radius 1 meter. The electrostatic force exerted on the electron can cause the electron to oscillate through the center of the ring. Find the frequency in Hertz of small-amplitude oscillation of the electron through the center of the ring.

Solution :

The magnitude of the electric field at a point on the z - axis is given by :

Force on the electron is

Now if z is very small,

∴

Comparing the equation with

By analogy,

The electric field on the axis of a square is given by

If we assumed that z << a

here,

d. platinum would have the greatest temperature increase because it has the lowest specific heat.