Question

A charge $Q$ is uniformly distributed over a large plastic plate. The electric field at a point $P$ close to the centre of the plate is $10V{m}^{-1}$ . If the plastic plate is replaced by a copper plate of the same geometrical dimensions and carrying the same charge $Q$ , the electric field at the point $P$ will become.

Answer 1

$\text{Step 1: Electric field due to a uniformly charged plate}$

Electric field at a point $P$ close to the centre of the plate:

$E=\frac{\sigma }{2{\epsilon }_0}$

Where $\sigma =\frac{Q}{A}$ is the surface charge density

$\text{Step 2: Electric field due to copper plate}$

Both Copper plate and Plastic plate have the same charge and same dimensions.

Therefore, surface charge density $\left(\sigma \right)$ would remain same in both cases.

Hence Electric field at point $P$ will be same due to both the sheets.

$\therefore E=10V{m}^{-1}$