A hollow charged conductor has a tiny hole cut into its surface. Show that the electric field in the hole is \frac{\sigma}{2 \epsilon_{0}} \hat{n}, where \mathrm{n}^{\hat{ }} is the unit vector in the outward normal direction and \sigma is the surface charge density near the hole.
A hollow charged conductor has a tiny hole cut into its surface. Show that the electric field in the hole is \frac{\sigma}{2 \epsilon_{0}} \hat{n}, where \mathrm{n}^{\hat{ }} is the unit vector in the outward normal direction and \sigma is the surface charge density near the hole.

Solution:

If we assume that the hole has been filled, then Gauss’s formula may be used to calculate the electric field intensity at a location near to the surface of the conductor, where

Flux, \phi=E . d s=\frac{q}{\epsilon_{0}}

q=\sigma x d s

here, \sigma is the surface charge density

ds is the area of the Gaussian surface

\mathrm{Eds}=(\sigma \mathrm{x} \mathrm{ds}) / \mathrm{\epsilon}_{0}

\mathrm{E}=\sigma / \mathrm{E}_{0}

=\frac{\sigma}{\epsilon_{0}} \hat{n}

Let E_{1} be the electric field due to the hole and E_{2} is the electric field due to the rest of the conductor. \mathrm{E}<em>{1} and \mathrm{E}</em>{2} are opposite in direction and equal in magnitude since the total electric field inside the conductor is zero.

\left|E_{1}\right|=\left|E_{2}\right|-(1)

The electric field E=\sigma / E_{0} is due to the superposition of E_{1} and E_{2}.

E=E_{1}+E_{2}

From equation (1) we know \mathrm{E}<em>{1}=\mathrm{E}</em>{2}

Therefore, E=2 \mathrm{E}_{1}

E_{1}=E / 2

Therefore, the electric field in the hole

\mathrm{E}<em>{1}=\frac{\sigma}{2 \epsilon</em>{0}} \hat{n}