Application of Gauss' Law: Feynman's Physics Explained

Feynman Vol II9-10

Gauss's law is a powerful shortcut for finding electric fields where there is symmetry, avoiding hard integrals. For a uniformly charged sphere, symmetry says the field must point straight out; draw an imaginary spherical surface and Gauss's law instantly shows the outside field is the same as if all the charge sat at the center. It also proves the field inside a hollow charged conductor is exactly zero — a very sensitive test of the inverse-square law.

The big idea

Symmetry plus Gauss's law turns hard problems into easy ones.

Think about it

Why are you safe from lightning inside a metal car? (Think about the field inside a hollow conductor.)

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