(a)[1]
What does electric field strength mean?
(b)[2]
An isolated metal sphere A, with radius $26\,\text{cm}$, carries a positive charge. Electrical breakdown (a spark) happens when the electric field strength at the sphere’s surface goes above $2.0 \times 10^{4}\,\text{V m}^{-1}$. Calculate the greatest charge $Q$ that can be held on the sphere.
(c)[2]
A second isolated metal sphere B, which also has charge $+Q$, has a radius of $52\,\text{cm}$. Calculate the additional charge, in terms of $Q$, that can be stored on this sphere before electrical breakdown takes place.