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## Homework Statement

So the question states that we have a hollow metal sphere of radius 2cm that is charged up. We take the breakdown field of air to be 1MV/m. We are asked to:

a) Calculate the maximum amount of charge which can be placed on the sphere.

b) Calculate the maximum potential on the surface of the sphere.

## Homework Equations

[itex]E = \frac{Q}{4\Piε_{0}r^{2}}[/itex]

## The Attempt at a Solution

a) [itex]1\cdot10^{6} = \frac{Q}{4\Piε_{0}0.02^{2}}[/itex]

So we get Q as being [itex]4.4\cdot10^{-8}C[/itex]

However, I'm stuck with what to do next to get the potential. I'm not entirely sure I understand the question? Is it the potential between that space on the surface and the center of the sphere?

I know the answer (or at least it is given as 20kV) but I'm not sure how to arrive at that answer.

Cheers