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2. Electric Potential and Capacitance
medium
A positive point charge $q$ is placed at a distance $2 R$ from the surface of a metallic shell of radius $R$. The electric field 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
$\frac{1}{4 \pi \varepsilon_0} \frac{q}{R^2}$
Solution

(b)
$\vec{E}_{ int }+\vec{E}_{ ext }=0$
$\vec{E}_{ int }=\vec{E}_{ ext }$
$\vec{E}_{ int }=\frac{k q}{9 R^2}$
Standard 12
Physics