A thin charged spherical shell of radius \(10\,cm\) has a uniform surface charge density of \(20\,pC/cm^{2}\). The electric potential at a point \(8\,cm\) from the centre of the shell is:
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Inside a uniformly charged spherical shell,
\[
\boxed{E=0}
\]
but
\[
\boxed{V=\frac{kQ}{R}}
\]
which is constant everywhere inside the shell.
Do not use \(V=\dfrac{kQ}{r}\) for points inside a spherical shell.
The total charge on the shell is $Q = \sigma \times 4\pi r^2 = 10^{-5} \times 4\pi \times (0.1)^2 \approx 1.257 \times 10^{-6}$ C. Treating the shell as a point charge for $R = 0.20$ m outside, $E = kQ/R^2 \approx 282$ N/C directed radially outward.