Question

A charge of $5\times {10}^{-10}C$ is given to a metal cylinder of length 10 m, placed in air. The electric intensity at a distance of 0.2 m from its axis is :

• A. 4.5 V/m
• B. 45 V/m
• C. 450 V/m
• D. 100 V/m

Answer 1

The correct option is A 4.5 V/m

Given,

$r=0.2m$

$l=10m$

$Q=5\times {10}^{-10}C$

The linear charge density of the cylinder is,

$\lambda =\frac{Q}{l}$

$\lambda =\frac{5\times {10}^{-10}}{10}=5\times 1^{-11}C/m$

The electric field intensity at point P is given by

$E=\frac{\lambda }{2\pi r{\epsilon }_0}$

$E=\frac{5\times {10}^{-11}}{2\times 3.14\times 0.2\times 8.85\times {10}^{-12}}$

$E=4.5V/m$

The correct option is A.