Define capacitance in words.
An isolated metal sphere has radius $r$. It is charged to potential $V$, and the sphere carries charge $q$. Since the charge can be regarded as acting as a point charge at the centre, state an expression for the sphere’s potential $V$ in terms of $r$ and $q$.
This isolated sphere has capacitance. Using your answers to (a) and (b)(i), show that the sphere’s capacitance is proportional to its radius.
The sphere in (b) has capacitance of $6.8\,\text{pF}$ and is charged to a potential of $220\,\text{V}$. Calculate the radius of the sphere.
An isolated metal sphere has radius $r$. When it is raised to potential $V$, the sphere carries charge $q$. The charge may be treated as a point charge at the centre of the sphere.
The sphere in (b) has capacitance $6.8\,\text{pF}$ and is raised to a potential of $220\,\text{V}$. Calculate
the charge on the sphere, in coulomb.
A second uncharged metal sphere is brought up to the sphere in (c) so that they touch. The combined capacitance of the two spheres is $18\,\text{pF}$. Calculate
the potential of the two spheres.
the change in the total energy stored on the spheres as they touch.