Define capacitance.
An isolated metal sphere has a radius 
. When charged to a potential 
, the charge on the sphere is 
. The charge may be considered to act as a point charge at the centre of the sphere.
State an expression, in terms of and , for the potential of the sphere.
This isolated sphere has capacitance. Use your answers in (a) and (b)(i) to show that the capacitance of the sphere is proportional to its radius.
The sphere in (b) has a capacitance of 
and is charged to a potential of 
. Calculate
the radius of the sphere,
the charge, in coulomb, on the sphere.
of the sphere is shown to be proportional to its radius 
.
.
