Electrostatics deals with forces between charges at rest. But if there is a force on a charge, how can it be at rest? My guess is that charges is being kept at rest by some unspecified forces that opposes the net Coulomb force on charge. So, what could be the so called "force"?
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asked Sep 14, 2015 at 9:36
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$\begingroup$ Nice question. If there is a low negative electrostatic potential, electrons do not fly away from a charged, but isolated plate. Is it somehow a confinement situation? $\endgroup$– HolgerFiedlerCommented Sep 14, 2015 at 10:24
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2$\begingroup$ Uh...the charges are usually fixed at their positions by other forces. It depends on the electrostatic situation what the opposing force exactly is. $\endgroup$– ACuriousMind ♦Commented Sep 14, 2015 at 11:50
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1 Answer
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Think of Electrostatics as interaction of charges in equilibrium after they have already dislocated and can't go anywhere else.
Keep in mind that charges in materials can have different origins.
In metals electrons move freely from atom to atom and in presence of external electric field relocate themselves in a way to reduce external field.
Dielectrics do not have free charges, but have dipoles which are represented either by displaced electron clouds of atoms or by polar molecules. If placed in electric field these dipoles stay at fixed positions but reorient themselves also in the way to oppose electric field.
If you bring two oppositely charged metallic spheres close to each other, charges will redistribute themselves and remain static.
