Hi, I'm trying to teach myself electricity and magnetism (and it's not easy!) and I'm not sure I understand flux...(adsbygoogle = window.adsbygoogle || []).push({});

For one thing, why is the flux through a closed surface zero if there is no charge inside of the surface (but there IS one outside)?

Another thing I'm not really sure about this either; why the flux through a closed surface is equal to 1/epsilon times ∫ ρ dv. That is, why the flux through any closed surface is independent of that surface's shape or size! One way I have of thinking about this (which may be completely wrong, I don't know), is this: The electric field decreases over distance as 1/r^{2}, but the surface area will also be increasing (this only works if it increases by the same proportion), so when a bigger surface surrounds a charge, the electric field will decrease while the surface area will increase, so the flux will stay the same. Is this a good way of thinking about it, or is it completely wrong?

Thank you

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# Flux through a closed surface

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