I'm revising for my exam and got stuck in the following questions. Please help.(adsbygoogle = window.adsbygoogle || []).push({});

1) An isolated spherical conductor of radius r is charged to a potential V. The total electrical energy stored is _______.

This is an MC question and the answer is V^{2}(2*pi*ε_{o}*r)

I only know energy stored = Qq/(4*pi*ε_{o}*r) and V=Q/(4*pi*ε_{o}*r)

2)A positively-charged metal sphere A of radius a is joined by a conducting wire to an uncharged metal sphere B of radius b placed far away from the first sphere. THe ratio of the surface charged density on sphere A to that on sphere B is ______.

The answer is b/a.

Well, I know surface area of A :surface area of B = a^2:b^2. How can I get the answer b/a ?

Thanks in advance.

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