Question

A spherical conductor of radius 2 cm is uniformly charged with 3 nC, What is the electric field at a distance of 3 cm from the centre of the sphere?

• A. $3\times {10}^{6}V{m}^{-1}$
• B. $3V{m}^{-1}$
• C. $3\times {10}^{4}V{m}^{-1}$
• D. $3\times {10}^{-4}V{m}^{-1}$

Answer 1

The correct option is C. $3\times {10}^{4}V{m}^{-1}$.

Given : $Q=3$ nC $=3\times {10}^{-9}C$

$d=3$ cm $=0.03$ m

Electric field at a distance of 3 cm,

$E=\frac{kQ}{d^2}$

where $k=9\times {10}^{9}N{m}^2/C^2$

$\therefore$ $E=\frac{9\times {10}^9\times 3\times {10}^{-9}}{(0.03{)}^2}=3\times {10}^{4}V/m$.