Level 1: Field Is Zero Inside a Charged Metal Sphere: Is the Potential Zero Too?
A charge inside an uncharged shell.
A point charge +q is placed at the centre of an uncharged, isolated hollow metal sphere. At a distance r outside the sphere, the electric field is:
The charge inside induces −q on the inner surface of the sphere. Because the sphere is uncharged overall, an equal +q appears on its outer surface, spread evenly over it.
Outside, the field is kq/r², exactly as if the sphere were not there. A metal shell shields its inside from charges outside, not the outside from a charge within, unless the shell is earthed.
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