There is a good chance that you, like I, have tried rubbing a balloon against your sweater or hair and sticking it to a wall. This is pretty cool to play with, but have you ever thought about why this works? I hadn’t and that’s why I found this week’s technology project so interesting.

A balloon is an insulator, meaning that it does not conduct electricity. When it is rubbed against a sweater it collects up electrons and stored it inside the ballon, building up static electricity. To test this we built electroscopes.

Basically, an electroscope is a device that detects static electricity. As you can see in the picture, we used a glass cup or jar, a piece of cardboard (instead of a lid), aluminum foil, and some copper wire. The first thing we did was trace the top of a jar onto a piece of cardboard and cut it out. Secondly, we bent one end of the wire into a hook and poked the straight end through the cardboard. Next, I put two small pieces of aluminum foil onto the end of the hook. Making sure that the wire and the aluminum foil were not touching any of the glass inside the jar, I taped the cardboard onto the top of the jar.

Next comes the exciting part; the experiment! For this part, I needed a ballon and a piece of felt.  After rubbing the felt on the balloon for about a minute, I held the side that I had rubbed the felt on close to the top of the wire, and like magic, the two sheets of aluminum foil separated, just like in the picture. This is because the negatively charged electrons that I built up in the balloon were sent down through the copper wire and into both aluminum foil sheets. Like charges repel, and this electroscope is no different. Because both pieces of the foil had become negatively charged, they separated from each other.