Question

A positive point charge $q$ is placed at a distance $2\, R$ 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. $\frac{1}{4 \pi \varepsilon_{0}} \frac{q}{9 R^{2}}$
• C. $\frac{1}{4 \pi \varepsilon_{0}} \frac{q}{4 R^{2}}$
• D. $\frac{1}{4 \pi \varepsilon_{0}} \frac{q}{R^{2}}$

Answer 1

Answer: (B)

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