Physics

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Video

Materials

• 1 soda can
• 1 balloon

Short explanation

The balloon takes electrons from the hair or clothes and thus becomes negatively charged. As the balloon approaches the soda can, it makes one side of the can positively charged. Since different charges attract each other, the can is now pulled toward the balloon.

Long explanation

When two materials come in contact with each other, there is always a chance that the atoms in one material take electrons from the atoms of the other material. When you rub the balloon against your hair or clothes, electrons will jump from the hair or clothes to the balloon. This makes the balloon negatively charged, because electrons have a negative charge. The hair or clothes that now lacks electrons is thus positively charged. Hair with a positive charge stand up, because all hairs repel each other.

As the balloon comes close to the can, electrons in the metal will be repelled by the electrons in the balloon. That is because equal charges repel. The electrons do not leave the soda can, but end up further inside the soda can, i.e. away from the balloon. The surface of the soda can facing the balloon is now positively charged. Because the balloon is negatively charged and one side of the can is now positively charged at the surface, they will attract each other.

If the balloon touches the soda can, they will stick to each other, again because of this attraction. Because the soda can is a bad conductor, few electrons to flow from the balloon to the soda can and equalize the charge difference between them.

This is an example of static electricity, i.e. charged particles that, without flowing anywhere, still affect each other with forces.

Over time, the "magical power" of the balloon will diminish. This is because excess electrons leave the balloon in small currents to the air.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you hold the balloon further from the soda can?
• What happens if you place the soda can on a carpet?
• What happens if you try to roll the soda can uphill?
• What other things can you move with the help of a charged balloon?

Variations

The balloon can attract many other materials. If you move it toward a water jet, the water jet will bend. You can also spread small pieces of paper from a hole punch on the table and see how the balloon attracts them.

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