Question

Find the electric field at point $\text{P}$ as shown in figure due to an infinite long uniformly charged non-conducting thick sheet.

• A. $10\text{N/C}$
• B. $20\text{N/C}$
• C. $30\text{N/C}$
• D. $40\text{N/C}$

Answer 1

The correct option is B $20\text{N/C}$

Given:
Thickness of sheet, $d=4\text{cm}=0.04\text{m}$
Distance of point $\text{P}$ from mid-line of sheet, $x=6\text{cm}=0.06\text{m};$
Charge density, $\rho =9{\text{nC/m}}^3;$

Here, $x>\frac{d}{2}$

We know that the electric field for a point outside the thick sheet is given by,
$E=\frac{\sigma }{2{ϵ}_0}=\frac{\rho d}{2{ϵ}_0}$

$\Rightarrow E=\frac{9\times {10}^{-9}\times 0.04}{2\times 9\times {10}^{-12}}=20\text{N/C}$

So, option $\left(b\right)$ is correct.