Here we’ll explore the power of static electricity with TWO activities: we’ll separate pepper from salt, and bend water!
What is Static Electricity?
A static charge occurs when there is an imbalance between positive and negative charges on the surface of a material – in other words, it is the build up of an electrical charge on the surface of an object. It’s called “static” because the charge remain in one spot.
We experience static electricity all the time! If you drag your socked feet while you walk on the carpet, your feet rub electrons off the carpet, leaving you with a slightly negative static charge. When you then touch a doorknob (or your brother or sister!), you get a shock as electrons jump from you to the doorknob, which conducts electricity. A buildup of static electricity inside a storm cloud is what causes lightning. We witness static electricity all the time!
Let’s look at a few other ways we can use static electricity to create some interesting results! You can also use these as magic tricks – you and I know it’s just the magic of science at work, but your audience will still be impressed!
Activity 1: Separate Salt from Pepper Using Static
- Plastic hair comb
- Add enough salt to your bowl to cover the entire bottom surface. Add a spoonful of pepper sprinkled across the top of the salt (use about ½ the amount of pepper than you used of salt). Mix the salt and pepper together in your bowl.
- Run the plastic hair comb through your hair several times. This will create a static charge on the comb.
Make a prediction! What do you think will happen when you hold the charged comb over the bowl? Once you’ve made your predication, take the charged hair comb and hold it over the bowl. What happens? The pepper should attach to the plastic hair comb!
The STEM Behind the Fun
What is a static charge?
A static charge occurs when there is an imbalance between positive and negative charges on the surface of a material.
Why does running the plastic comb through your hair build up a static charge?
Every material is made up of small particles called atoms which are made up of even smaller particles called protons, neutrons, and electrons. Protons represent a positive charge, neutrons represent no charge, and electrons represent a negative charge. The protons and neutrons are in the center of the atom, called the nucleus, while the electrons orbit around the outside. When you brush the plastic comb through your hair, the electrons leave the atoms on your strands of hair and move onto the comb, causing a buildup of negative charge on the comb.
Why does the pepper attach to the comb but not the salt?
The pepper attaches to the comb because opposite charges attract! Just like the comb, the salt and the pepper are each made up of tiny atoms made up of protons, neutrons, and electrons. The electrons in the pepper are more easily able to move around than the electrons in the salt. Because opposite charges (positive/negative) attract and same charges (positive/positive or negative/negative) repel, all of the electrons in the pepper atoms move away from the comb leaving one side of each flake of pepper more positive than the other. The positive side of the pepper is attracted to the negative comb. Pepper is also lighter than salt, so the pepper is able to jump up onto the comb while the salt remains in your bowl.
Activity 2: Bend Water with Static
- Plastic hair comb
- Water faucet
- Charge the plastic comb with static electricity by running the comb through your hair.
- Turn on your faucet so that a small stream of water is coming out.
- Make a prediction! What do you think will happen when you hold the charged comb near the stream of water? Once you’ve made your prediction, find out what happens! Take the charged hair comb and hold it close to (but not touching) the small stream of water coming from the faucet. What happens? The thin stream of water should bend towards the comb!
The STEM Behind the Fun
Why does the stream of water bend towards the comb?
The stream of water bends towards the comb because opposite charges attract! The water is also made up of tiny atoms that are made up of protons, neutrons, and electrons. When the negatively charged comb is moved near the stream of water, the electrons in the water move away from the comb, leaving one side of the stream of water more positive than the other. The positive side of the stream of water moves towards the comb because of the attraction between the opposite charges!