Light By Friction
What you need
- A piece of Saran Wrap or clear plastic wrap
- A piece of fake fur (we don't use real fur)
- A piece of wool
- A piece of cotton
- A piece of other types of cloth
- A fluorescent lighting tube (an old one will do)
What to do?
- In a dark room, hold the tube carefully in one hand and hold the piece of material in the other. Rub the fluorescent tube up and down vigorously with the saran wrap. Watch what happens.
- Try this again and again with the other pieces of fur and cloth. Watch what happens.
What you'll discover
A fluorescent tube will glow when there is an electric field inside the glass. Normally this occurs when a current of electricity is passed through the tube when a wall switch is turn on. The electric field causes some electrons to separate from the nuclei of the gas. When the electrons fall back into their regular places, they cause the tube to glow. This is called a "ground state."
When you rub up and down with each of the pieces or cloth, fur or plastic, you create static electricity. This static electrical field excites the electrons.
Does the tube glow brighter when a different material? Why do you think this is?
Warning: the electricity being generated is not dangerous. But be VERY careful with the fluorescent tube. If dropped, you could get cut with broken glass. Also, fluorescent lights contain small amounts of mercury, so if it does break, put on a pair of disposable gloves, clean up the pieces with a damp paper towel, and seal everything in a plastic bag or in a container, such as an old margarine tub. The bagged pieces should be brought to a hazardous waste site or bulb collection site.
Reprinted with the permission of the California Energy Commission. © 1994-2008 California Energy Commission.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.