Episode 9: Electric Balloons
We’re sure this electrifying demo will be a positive experience for you and your family. Find out about electric charges and how they can be used to attract and repel. We hope it doesn’t rub anyone up the wrong way…
Before you start
These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.
What you’ll need
- Two balloons
- Sticky tape
- A woolly jumper or glass
- Ball of string/ wool/ thread
- A full head of hair (optional)
What to do
This experiment works best on a dry day. Water vapour in the air makes the balloons discharge as you’re trying to charge them, so for this experiment humidity is definitely the enemy!
- Inflate the balloons and tie them off.
- Tie string around the knot of each balloon.
- Find somewhere in your house to tape the balloons up so that they have space to move and so that your family can reach them. You might need to adjust this bit based on the heights of your family, so make sure you have enough string.
- Tape the balloons so that they just touch when you let them hang straight down.
- On the spot where the balloons have just been touching, rub each balloon on your jumper or a glass or even your hair. In fact, it’s a good idea to rub them all over just in case the balloons twist or turn in mid-air.
- Notice that where the balloons were touching, they aren’t any more. You can even push one balloon towards the other and the other one will move away.
What to talk about
- Have you ever seen someone make their hair stand up by rubbing it with a balloon before?
- If you listen closely to the balloons can you hear them crackle? What do you think could be making the noise?
What’s going on?
Everything is made up of atoms that have a positively charged centre and negatively charged outside made of particles called electrons. Each atom has the same amount of positive and negative, so usually the charges cancel out and we don’t notice them.
When you rub two things together you can move the negatively charged electrons from one material to another. Some materials are more likely to lose their electrons than others, in our experiment the rubber balloon is much better at holding onto its electrons than the other materials, so as the balloon is rubbed it gains electrons and the thing doing the rubbing loses them.
As the balloon gains more and more electrons it ends up with a negative electric charge. The glass/jumper/hair in our experiment has lost its electrons so now has the opposite charge – a positive electric charge.
Opposite charges attract and so there’s a small force that pulls the balloon towards the jumper or glass. If you rub a balloon against your hair and then lift it up, the attractive electrical force is large enough that it can overcome the force of gravity pulling down and it becomes a hair-raising experience!
When you rub both balloons, both end up with negative charge. Similar charges repel so the balloons push away from each other. You can even use one balloon to push the other around!
Finally, there needs to be a way for all those extra electrons to discharge somehow. In physics this is called earthing or grounding, and works by providing a path that the extra electrons can travel along to the ground. This can either be by touching the balloon to the ground directly or touching it to something that electrons can travel through, like your body or the water in the air.
If this experiment has sparked your curiosity here are a few more things to try:
- Now that you know that opposites attract, try charging up a balloon using different materials and see how long and how well it sticks.
- Experiment with grounding the balloons. How long does it take for the balloons to discharge and come back together if you:
- Don’t touch them at all
- Flick or spray water into the space between the balloons
- Touch each balloon with your finger once?
Did you know?
The ancient Greeks rubbed amber with fur to investigate what happened. That’s where the negatively charged particles gets their name. In ancient Greek, the word for amber was “elektron”.
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