A metalic spherical shell has an inner radius `R_1 and ` outer radius `R_2` . A charge Q is placed at the centre of the spherical cavity. What will be surface charge density on (i) the inner surface and (ii) the outer surface?

Explanation

Due to presence of a charge Q at the centre of spherical cavity chrage -Q is induced on the inner surface of shell and a charge +Q is induced on the outer surface as shown in
(i) ` therefore ` Surface charge density on inner surface `sigma_1 =(-Q)/(A_1) =(-Q)/(4piR_1^(2)) `
(ii) `therefore ` Surface charge density on the outer surface `sigma_2=(+Q)/(A_2) =+(Q)/(4pi R_2^(2))`
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