Electric Charge and Charge Quantization

Every object's charge is some whole multiple of e = 1.602x10⁻¹⁹ coulombs, the charge on a single proton or electron. You never find half an electron's worth of charge sitting on something. This is charge quantization, and it means charge is countable, like marbles, not pourable like water. When you say an object has a charge of -3.2 nC, you're really saying it's holding a specific, countable surplus of electrons.

Rubbing a balloon on your hair doesn't manufacture charge. Both the balloon and your hair start neutral, with equal numbers of protons and electrons. Friction strips electrons off one material and deposits them on the other, because some materials hold their outer electrons more loosely than others. Your hair gives up electrons to the balloon, so the balloon ends up with extra electrons (negative) and your hair ends up short of electrons (positive). Add up the charge on both objects together and it's exactly what it was before you rubbed them: charge is conserved, just redistributed. The balloon sticks to the wall afterward because its surplus electrons repel the wall's surface electrons slightly, pushing them back and leaving the wall's surface net positive right where the balloon touches, so the two attract.

This idea of charge as a discrete, conserved quantity on individual objects is the starting point for everything after it in the unit. Once you know charge exists in countable amounts on point-like sources, you can ask how that charge reaches out into space around it, which is exactly the electric field, and later how fields from many charges add up, which is where Gauss's law earns its keep.