Question

 An isolated sphere has a capacitance of 50pF. 

(a) Calculate its radius. 

(b) How much charge should be placed on it to raise its potential to 10⁴ V?

Answer 1

 For sphere, radius R is given by C = 4πε₀R . To raise the potential to 10⁴ V, the charge to be placed on sphere is given by Q = CV.

(a) The capacitance of an isolated sphere is