The Science Behind the Sneaky Can

Have you ever rubbed a balloon on your hair and watched your hair stand on end? Or received a tiny shock after walking across carpet?

You have already experienced static electricity.

In this experiment, you used that same invisible force to make a drink can roll across a table without touching it. It might look like magic, but it's actually a fascinating example of electricity and forces working together.

How Does Rubbing a Balloon Create Electricity?

Everything around us is made from tiny particles called atoms. Atoms contain even smaller particles, including electrons, which carry a negative electrical charge.

When you rub the balloon on your hair, jumper or cloth, some of these electrons move onto the balloon.

The balloon now has an extra negative charge. This build-up of electric charge is called static electricity because it stays in one place instead of flowing like the electricity in power points and batteries.

Why Does the Can Start Rolling?

Even though the balloon never touches the can, it still affects it.

As the charged balloon comes close, the tiny electrical charges inside the aluminium can shift slightly. This creates a small positive region on the side closest to the balloon.

Because opposite electrical charges attract, the balloon pulls on the can.

As you slowly move the balloon away, the can keeps following it, making it look almost as though an invisible string is attached.

Not All Materials Behave the Same Way

You probably noticed that some balloons worked better than others.

The amount of static electricity depends on many factors, including:

• what material you rub the balloon with

• how long you rub it

• the humidity in the air

• the type of balloon you use

Dry days usually produce much stronger static electricity because moisture in the air allows electrical charges to escape more easily.

Static Electricity Is Everywhere

Static electricity isn't just something you see in science experiments.

Scientists and engineers use the same ideas in many surprising ways:

• photocopiers and laser printers

• air cleaners that remove dust

• electrostatic paint spraying

• protecting delicate electronic equipment

• lightning during thunderstorms

The same invisible force that moved your can also helps power technology used every day.