Polarization and Grounding

A charged comb held near bits of paper does not give them any charge. Instead the comb's electric field reaches into the paper and shoves its electron clouds around. In an insulator the electrons cannot leave their atoms, but they can shift slightly, so one side of each molecule becomes a little negative and the other a little positive. Line up enough molecules this way and the whole object has a negative face and a positive face, even though it is still neutral overall. That's polarization: charge rearranged, not created.

The attraction happens because the induced charge of opposite sign sits closer to the source than the induced charge of the same sign. Coulomb's law cares about distance, so the nearer opposite charge pulls harder than the farther like charge pushes. The net force is attractive even though the object carries zero net charge, which is exactly why a polarized object never ends up charged itself — equal amounts of positive and negative charge are just separated, and they still add to zero.

Grounding is a different process: it actually changes an object's net charge by connecting it to the Earth, a vast conductor that can absorb or supply electrons without noticeably changing itself. Touch a charged conductor with a ground wire and excess charge flows along it until the conductor is neutral. In a metal, free electrons make this redistribution and flow far easier than in an insulator, which is why grounding works on conductors and sets up the next idea: conductors in equilibrium have zero field inside and all excess charge sitting on their surface.