Question

The electric field at a point $5cm$ from a long line charge of density $2.5\times {10}^{-6}c{m}^{-1}$ is :

• A. $9\times {10}^{3}N{C}^{-1}$
• B. $9\times {10}^{4}N{C}^{-1}$
• C. $9\times {10}^{5}N{C}^{-1}$
• D. $9\times {10}^{6}N{C}^{-1}$

Answer 1

Answer: (C)

$9\times {10}^{5}N{C}^{-1}$

The electric field at a distance r from the long wire is

$E=\frac{1}{4\pi {ϵ}_0}\frac{2\lambda }{r}=9\times {10}^9\times \frac{2\times 2.5\times {10}^{-6}}{5\times {10}^{-2}}=9\times {10}^{5}N{C}^{-1}$