Charging by Friction
Blow up a balloon and hang it up with a thread. Get a glass rod and rub it on the balloon.
When you then move the rod away, the balloon would be attracted to the rod.
Blow up another balloon and hang it next to the first one. Rub the glass rod on both balloons.
When you remove the rod, the two balloons would repel each other.
During the rubbing, some electrons move from the glass rod to the balloon. The balloon has an excess of electrons. We say that it is negatively charged. This glass rod loses some electrons, and become positively charged.
The glass rod attracting the balloon shows that positive charges attract negative charges. The balloons repelling each other shows that one negative charge repels another negative charge.
When two objects in the following list are rubbed together, the one higher on the list becomes positively charged, and the one lower down becomes negatively charged.
- Human Hands (must be very dry)
- Leather
- Rabbit Fur
- Glass
- Human Hair
- Nylon
- Wool
- Fur
- Silk
- Aluminum
- Paper
- Cotton
- Wood
- Amber
- Hard Rubber
- Polyester
- Styrofoam
- Polyurethane
- polythene (e.g. plastic bag)
- PVC (e.g. plastic pipe)
- Silicon
- Teflon