An insulated metal sphere of radius 
is situated in a vacuum. The charge 
on the sphere may be considered to be a point charge at the centre of the sphere.
State a formula, in terms of and , for the potential 
on the surface of the sphere.
Define capacitance and hence show that the capacitance 
of the sphere is given by the expression
An isolated metal sphere has radius 
. Use the expression in (a)(ii) to calculate the capacitance, in picofarad, of the sphere.
.
