For example , if you rub a plastic ruler on your jumper you can use it to pick up small pieces of paper. This is because the charges in the paper turn around until the positive charges are pointing towards the negatively-charged rod. The attractive force between the different charges is enough to pick up the bits of paper. It is only insulators that can be charged up in this way. If we tried to charge up a conductor , like a metal rod, by rubbing it with a cloth, any extra charges that moved on to the metal would flow away.
Electrostatic charges can lead to electric shocks and sparks.
These sparks can be quite small, like the sparks you can see on your clothing as you get undressed, or as large as a flash of lightning. Sparks are caused when there is a large imbalance of electric charges . If you pull a jumper over your head, the friction may cause the jumper to gain an excess of electrons. These electrons repel each other. Even though air is an insulator , it is possible for the electrons to travel through it, if the charge imbalance is large enough.