Why does a plastic rod have a negative charge after being rubbed with a piece of fur??
The road gains electrons from the fur. Protons and neutrons are held within the nucleus of the atom by powerful forces, and cannot be transferred between atoms. In fact, the nucleus contains so much force/energy, that when it starts to break apart and decay, as unstable nuclei do, the atom becomes radioactive. So all that can be transferred between atoms and molecules are electrons. Electrons are negative. So if the plastic rod has become negatively charged, you know it must have gotten more electrons than it had previously, because electrons are negative so obviously gaining electrons would make the rod more negative. So the rod gained electrons from fur.
