Question

Find the magnitude of the electric field at a point 4 cm away from a line charge od density $2\times 10-11C{m}^{-1}$

Answer 1

Drawing the electric field around line charge , we find a cylinder of radius

$4\times {10}^{-2}m$

Given $\gamma$ =linear charge density

$2\times 10-6C/m$

We know,

$E.ds=\frac{q}{{\in }_0}$

$E.2\pi rl=\frac{\gamma l}{{\in }_0}$

$\therefore E=\frac{\gamma }{2\pi r{\in }_0}$

$=\frac{9\times 2\times {10}^9\times 2\times {10}^{-6}}{4\times {10}^{-2}}$

$=9\times {10}^{5}N/C$