Activity: Static electricity

Talia with her charged-up balloon.

On SCOPE's electricity episode, you saw Talia use static charges. Here’s what she did. Watch the clip.

What you need

• A balloon
• Some puffed rice cereal
• A piece of cotton thread
• Glue
• A plastic rod (a knitting needle will do)
• Wool
• A steady flow of water.

What to do

Experiment 1

1. Glue a piece of puffed rice to one end of the piece of cotton.
2. Charge up the balloon by rubbing it on your head or against your jumper.
3. Hold the puffed rice on the cotton and move it near the balloon. What happens?

Experiment 2

1. Rub a plastic rod with some wool.
2. Turn on a tap to create a small steady flow of water.
3. Move the plastic rod near the water and watch what happens.

What's happening?

Have you ever been zapped when touching a doorknob, getting out of a car or climbing off a trampoline? You are actually getting an electric shock! But why?

In Experiment 1, the puffed rice swings towards the balloon because it is electrically attracted to it.

Rubbing the balloon against your hair or jumper charges the balloon, giving it a negative charge on the surface. The negative charge on the balloon then attracts the positive charges in the puffed rice, causing it to swing towards the balloon.

In the second experiment, the water appears to be bending towards the plastic rod. The negative charges on the surface of the rod attracts the positive charges in the water molecules and this pulls the water stream towards the rod, just as the balloon pulled the puffed rice towards it.

It is the same reason your hair is attracted towards a balloon you have just rubbed on it.

But why do you get an electric shock from jumping on a trampoline?

When you walk on carpet or jump on the trampoline you are building up an electric charge, just as we did when rubbing the balloon against a jumper. Sometimes our bodies become so negatively charged that the charge jumps to a metal object, such as a car door or even another person! When this happens, we experience an electric shock.

One of nature’s best examples of this phenomenon is lightning. Lightning is a bit like the rain clouds giving the earth an electric shock. It’s formed when air rubs against rain clouds. The rain clouds become so negatively charged that this charge jumps to the earth’s surface, and what do we see? A lightning bolt!