Question

A positive point charge $q$ is placed at a distance $2R$ from the surface of a metallic shell of radius $R$. The electric ield at centre of shell due to induced charge has magnitude

• A. Zero
• B. $\frac{1}{4\pi {\epsilon }_0}\frac{q}{9R^2}$
• C. $\frac{1}{4\pi {\epsilon }_0}\frac{q}{4R^2}$
• D. $\frac{1}{4\pi {\epsilon }_0}\frac{q}{R^2}$

Answer 1

Answer: (B)

${\vec{E}}_{\text{int }}+{\vec{E}}_{\text{ext }}=0$
${\vec{E}}_{\text{int }}={\vec{E}}_{\text{ext }}$
${\vec{E}}_{\text{int }}=\frac{kq}{9R^2}$