4^th Grade Scientists Explore

Positive & Negative Charges

We wanted to see if we what would happen if we put a balloon near dry gelatin before and after the balloon was rubbed with a piece of felt. Here’s how we did it and what we found out!

Materials

ê Balloon

ê Piece of dark paper

ê Small piece of felt

ê Dry gelatin

Procedure

ê First we put some gelatin on the dark paper. Then we put the balloon over the gelatin. Nothing happened!

ê Then, we rubbed the balloon with felt. When we put it near the gelatin, the gelatin moved! Some of it stuck to the balloon. If we held it just above the gelatin, we could see it reaching for the balloon. We also rubbed the balloon on our heads. This also made the gelatin move towards the balloon.

ê Finally, we touched the balloon with our hands. We kept putting our hands on the balloon several times. When we put the balloon above the gelatin, it did not move again!

Why did this happen?

When Mrs. Kanas gave us the gelatin and the balloon, they both had an equal number of positive and negative charges. So when we put the balloon above the gelatin, nothing happened. When we rubbed the balloon with the felt, friction caused negative charges to move from the felt to the balloon. Now the balloon had more negative charges than positive charges. We learned that opposite charges attract, or come together Now when we put the balloon over the gelatin, the extra negative charges attracted the positive charges in the gelatin.

Here are some pictures of us observing the negative charges attracting the positive charges.

Back to Mrs. Kanas’s Classroom Homepage

Created by: J. Kanas 2009