Electricity Explained

Getting Down To Basics

By Bruce W. Maki

Charges and Static Electricity

Normally an atom will have exactly as many electrons as protons. Protons have what we call a positive electric charge. Electrons have a negative electric charge. Neutrons have no charge.

When the number of electrons equal the number of protons, the atom is neutral. If an atom was given an extra electron, the atom has a negative charge.

If an electron is taken away from a neutral atom, then the atom will have a positive charge, because there are more positive protons than negative electrons.

If a negatively charged atom comes near a positively charged atom, they will be attracted to each other.

Two negative charges will repel each other, just like two positive charges will repel.

Sometimes an entire object can become charged. If you rub your feet on a carpet, your entire body will become charged. If you touch someone who is not charged, or a metal object like a door knob, you might notice a spark of static electricity. What happened?

The excess electrons in your body needed to go somewhere, and when you touch something that is not charged (like a large piece of metal) it absorbs the extra electrons suddenly. The electrons flow quickly through the tip of your finger into the object you touch. If you rub your feet on the carpet long enough you can build up a pretty big charge, and when you touch something else you will experience a pretty big (and possibly painful) discharge of electricity. The flow of electrons might be great enough that you can see a tiny spark and hear a snapping sound.