Question

Find electric field due to finite line charge at point $P$.

• A. $85\text{N/C}$
• B. $65\text{N/C}$
• C. $75\text{N/C}$
• D. $55\text{N/C}$

Answer 1

The correct option is C $75\text{N/C}$

Given:
$r=1\text{m};L=5\text{m}:\lambda =10\text{nC/m}=10\times {10}^{-9}\text{C/m}$

Using direct formula for electric field due to finite line charge,

$E_P=\frac{kQ}{L}[\frac{1}{r}-\frac{1}{r+L}]=k\lambda [\frac{1}{r}-\frac{1}{r+L}]$

$\Rightarrow E_P=9\times {10}^9\times 10\times {10}^{-9}[\frac{1}{1}-\frac{1}{1+5}]$

$\Rightarrow E_P=75\text{N/C}$

Hence, option $\left(c\right)$ is the correct answer.