Types of Charges and Their Interaction
In the above activity, one becomes positively charged and the other is negatively charged.And, these positive and negative charges behave in interesting ways.
Did you ever hear the saying that opposites attract?
Well, it's true. Two things with opposite, or different charges (a positive and a negative) will attract, or pull towards each other. Things with the same charge (two positives or two negatives) will repel, or push away from each other.
- Opposite charges attract each other. For example, a positive charge attracts a negative charge.
- Like charges repel each other. For example, a positive charge repels a positive charge and a negative charge repels a negative charge.
A charged object will also attract something that is neutral. Think about how you can make a balloon stick to the wall.
How does this happen? How does the simple rubbing together of two objects cause the objects to become charged and charged oppositely?
If you charge a balloon by rubbing it on your hair, it picks up extra electrons and has a negative charge. Holding it near a neutral object will make the charges in that object move. If it is a conductor, many electrons move easily to the other side, as far from the balloon as possible. If it is an insulator, the electrons in the atoms and molecules can only move very slightly to one side, away from the balloon. In either case, there are more positive charges closer to the negative balloon. Opposites attract. The balloon sticks. (At least until the electrons on the balloon slowly leak off.) It works the same way for neutral and positively charged objects.
So what does all this have to do with static (electric) shocks? Or static electricity in hair? When you take off your wool hat, it rubs against your hair. Electrons move from your hair to the hat. A static charge builds up and now each of the hairs has the same positive charge. Remember, things with the same charge repel each other. So the hairs try to get as far from each other as possible. The farthest they can get is by standing up and away from the others. And that is how static electricity causes a bad hair day!
You walk across the rug, reach for the doorknob and..........Ouch!!! You get a shock.
As you walk across a carpet, electrons move from the rug to you. Now you have extra electrons and a negative static charge. Touch a door knob and ZAP! The door knob is a conductor. The electrons jump from you to the knob, and you feel the static shock.
This type of generating positive and negative charges on a body is called Static Electricity.
We usually only notice static electricity in the winter when the air is very dry. During the summer, the air is more humid. The water in the air helps electrons move off you more quickly, so you can not build up as big a static charge.