Suppose I have a positively charged conductor with a cavity. There's a positive charge inside the cavity and the system has reached electrostatic equilibrium. Then there's negative charge surrounding the cavity and positive charge on the surface of my conductor. If I apply gauss law to the interior of the conductor I conclude that the electric field is zero at every point of my gaussian surface, and if it weren't so, then charged particles would be accelerating or whatever.

But my question is: why don't the atoms in the interior affect the electric field? I mean, even if the atoms are neutral (consider now a non-conducting material) they have charges inside that should somehow alter the electric field in the neighborhood.

What's going on?



1 Answer 1


This table should answer your question which is about intermolecular interactions. The largest distance that the electromagnetic forces can be effective for neutral atoms and molecules is in fractions of a nanometer.

When in classical distances then the electric field coming from neutral atoms is effectively zero. Nano structures though, if you make your cavity a nano structure, have to take it into consideration in calculations.

The forces are spill over forces, dipole, quadrupole, and higher poles due to the deformations of the atoms/molecules in their solid state formations, and are responsible for maintaining the solids, but the effective range is very small compared to bare charges.

  • $\begingroup$ Nice. So it's a matter of practicality then? Thank you for your answer. $\endgroup$
    – DLV
    Sep 15, 2014 at 3:44

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