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richyw
An isolated conducting sphere with radius \(R=6.85\text{cm}\) has charge \(Q=1.25nC\) a) how much potential energy is stored in the electric field of this charged conductor? b)what is the energy density at the surface of the sphere? c)what is the radius \(R_0\) of an imaginary spherical surface such that half of the stored potential energy lies within it?
my attempts: a)\[U=\frac{Q^2}{2C}=\frac{Q^2}{8\pi\epsilon_0R}\]b)\[u=\frac{1}{2}\epsilon_0E^2\]\[u=\frac{1}{2}\epsilon_0\left(\frac{1}{4\pi\epsilon_0}\frac{Q}{R^2}\right)^2\]\[u=\frac{Q^2}{32\pi^2\epsilon_0R^4}\] c) unsure!