Static electricity is a build-up of electric charge on the surface of an object. It happens when certain materials are rubbed together and tiny particles called electrons move from one surface to the other. The object that gains electrons becomes negatively charged, and the one that loses them becomes positively charged. These charged objects can attract or repel each other, which is why your hair stands up after you rub a balloon on it.
Rub a balloon on hair or a wool sweater and stick it to a wall. Use a plastic comb on dry hair and hold it near small bits of paper. Shuffle feet on carpet in socks and touch a metal doorknob to feel a spark. Discuss what is happening at each step.
Have you ever rubbed a balloon on your hair and watched your hair stand up and follow the balloon? Or felt a zap when you touched a doorknob after walking across a carpet? Both of these are caused by static electricity — a build-up of electric charge on the surface of objects.
Everything around you is made of tiny atoms, and inside every atom are even tinier particles. Protons carry a positive charge and stay locked in the center of the atom. Electrons carry a negative charge and can sometimes move from one atom to another. When you rub two materials together — like a balloon on your hair — electrons rub off one surface and stick to the other. The balloon gains extra electrons and becomes negatively charged. Your hair loses those electrons and becomes positively charged.
Once objects are charged, they behave a lot like magnets. Opposite charges attract — the negatively charged balloon pulls on your positively charged hair, making it reach toward the balloon. Like charges repel — each strand of your hair has the same positive charge, so they all push away from each other and stand on end. This attraction and repulsion is the electric force, and it works even without the objects touching.
The shock you feel at a doorknob happens because your body has built up excess electrons. Metal is an excellent conductor, so the instant your finger gets close, electrons jump across the tiny air gap as a spark. That spark is a miniature bolt of lightning. In fact, real lightning is static electricity on a massive scale — clouds build up huge charges from water droplets and ice crystals rubbing together, and the charge releases as a lightning bolt. Static electricity is the starting point for understanding all of electricity.