The Coulomb force is the electrostatic force between electric charges. For point charges in a uniform isotropic medium of permittivity , the force on charge from is , where points from the first charge to the second.
Equal charge signs give repulsion and opposite signs give attraction. The inverse-square dependence allows superposition to construct fields of extended charge distributions. Nearby conductors or spatially varying dielectrics can redistribute charge and alter the field, so the simple uniform-medium pair formula does not automatically solve those boundary problems.
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