# Lightning

## Activity Source:

### Background

Static electricity can be used to demonstrate the electricity of lightning. This activity will demonstrate the attraction of positive and negative charges and what happens when those opposite charges meet each other.

## Time Needed

One class period

### Materials Needed

• Foam plate
• Thumbtack
• Pencil with new eraser
• Aluminum pie pan
• Small piece of wool fabric

### Instructions

1. Push the thumbtack through the center of the aluminum pie pan from the bottom.
2. Push the eraser end of the pencil into the thumbtack. (The pencil becomes a handle to lift the pan.)
3. Put the foam plate upside-down on a table. Rub the underside of the plate with the wool for one minute. Rub hard and fast.
4. Pick up the pie pan using the pencil "handle" and place it on top of the upside-down plate
5. Touch the pie pan with your finger. If you don't feel anything when you touched the pan, try rubbing the plate again.
6. Try turning the lights out before touching the pan. Do you see anything when you touch the pan?

What happened when you touched the metal pie pan? What caused that? How do you think this experiment relates to the formation of lightning?

### What's Happening?

It's all about static electricity! Lightning happens when the negative charges (electrons) in the bottom of the cloud (and your finger) are attracted to the positive charges (protons) in the ground (and the pie pan). The resulting spark is like a mini bolt of lightning.

The accumulation of electric charges has to be great enough to overcome the insulating properties of air. When this happens, a stream of negative charges pours down towards a high point where positive charges have clustered due to the pull of the thunderhead.

The connection is made and the protons rush up to meet the electrons. It is at that point that we see lightning and hear thunder. A bolt of lightning heats the air along its path causing it to expand rapidly. Thunder is the sound caused by rapidly expanding air.