Sometimes, a large number of atoms in an object gain or lose electrons. When such a gain or loss happens, the entire object takes on an electric charge (then they're called ions). The term static electricity describes situations where objects carry electric charge.
Static electricity occurs, for example, when you rub a balloon on your shirt. The friction between the cloth and the balloon causes electrons to transfer from your shirt to the balloon. The shirt then has an overall positive charge because it has more protons than electrons. The balloon takes on a negative charge because it has extra electrons. The balloon will then stick to the shirt or to another surface, such as a wall.
Static electricity has many uses in homes, businesses, and industries. For example, the copying machines found in most offices are electrostatic copiers. They make duplicates of printed or written material by attracting negatively charged particles of toner (powdered ink) to positively charged paper. Static electricity is also used in air cleaners called electrostatic precipitators. These devices put a positive electric charge on particles of dust, smoke, bacteria, or pollen in the air. Negatively charged collector plates attract the positive particles out of the air.