An infinitely long thin straight wire has uniform linear charge density of 1/3 coul.${\mathrm{m}}^{-1}$. Then the magnitude of the electric intensity at a point 18 cm away is

Given Data: For an infinitely long wire, $\lambda =1/3coul.m^{-1} , r=18 \mathrm{cm}$

Formula Used: $E=\frac{2\mathrm{k}\lambda }{r}$

Detailed Solution:

The field due to an infinite linear charge density is,

$E=\frac{2\mathrm{k}\lambda }{r}$

$=\frac{2\times 9\times {10}^9\times 1/3}{18\times {10}^{-2}}$

$=0.33\times {10}^{11}{\mathrm{NC}}^{-1}$

Hence, the correct option is (A).