Bend Water with Static Electricity
Static electricity does more than shock you when you go to open a door, or attract dust to your furniture and clothes. It can actually bend a stream of water. This is a good science demonstration for kids because it shows how an electrically charged object attracts some things with a neutral charge.
Contents
Steps
Bending Water
- Run a nylon comb through your hair. Take a dry nylon (plastic) comb and run it through your hair about 10 times. Your hair must be dry as well. When the comb moves through your hair, it picks up electrons — tiny particles with an electric charge.
- If you don't have a comb, find a plastic spoon or an inflated balloon instead. Rub the object quickly against your hair, or a piece of fur, wool, or carpet. The friction from rubbing the two materials together knocks electrons loose from one object and onto the other.
- Turn on your faucet. Only let a very thin stream of water flow. It needs to be a smooth stream, not one that breaks up.
- Place the comb right next to the stream of water without touching it. If the comb (or spoon or balloon) picked up enough charge, the water will bend toward the comb as it falls. See "Why this works" below for an explanation.
- Understand how this works. Electrical charges come in two types, positive and negative. Those electrons that ended up on your comb have a negative charge, while water molecules have a positive charge on one side. Positive and negative charges pull each other closer together, so when the comb is close enough, the positive side of the water molecules get tugged in that direction.
- When the negatively charged comb comes near the water, it repels the electrons, so that the side of the water nearest the comb then has a positive charge. The attraction between this positive charge and the negatively charged comb results in a net force on the water, bending the stream.
Extra Experiments
- Experiment. Bend water again, but change the variables, one at a time. See how they affect the result. Can you explain why?
- Does the temperature of the water affect how much it bends?
- Does a bigger object make the water bend more?
- Does the material that the object is made of affect its ability to bend water?
- How does the strength of the stream flow affect how much it bends?
- Play with static electricity in other ways. Try rubbing an inflated balloon against your hair as fast as you can. Gently put the balloon against a bare patch of wall and let go. If the balloon picked up enough charge, it will stay there against the wall without falling.
- This works because the balloon weighs almost nothing, so gravity barely affects it. The electrical attraction between the balloon and the wall is strong enough to resist the pull of the whole world!
- You can also tear up tiny bits of paper and pick them up with the balloon.
- Learn about grounding. When trying this experiment, you might have put down the comb, then discovered it can't bend water anymore after you pick it up again. Some objects (especially metal ones) can suck up all the extra electrons with a touch, so your comb loses its charge. This is called "grounding." Scientists and engineers use grounding on purpose to protect themselves from electric shocks. You can too:
- Wait until a dry day, when it hasn't rained in a while. Static electricity builds up much faster when there is almost no water in the air.
- Find an object that often gives you a shock. This might be a car after you've been sitting in it for a long time, a metal door handle, or a playground slide.
- Before touching the object, poke it with something metal. (Or before getting out of the car, poke the metal frame.) This could be a coin, a key, or a metal pole. The electrons will quickly flow into the metal you're holding, then harmlessly into you. You can now touch the object without getting shocked.
- Sometimes, if a lot of electrons have built up, you can see a spark as they jump into the thing you're holding.
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Tips
- Static electricity is used in photocopiers. The document is recorded, and then a sheet of paper is "imprinted" with static electricity using that pattern. When toner is sprayed onto the paper, it only sticks to the areas with a negative charge.
- This will only work in dry conditions. Try to do this on a day with low humidity, and don't do it right after someone has taken a shower. When it's humid, everything gets coated in a thin film of water, which makes the transfer of electrons more difficult. The water molecules in that film (as well as in the air) capture electrons that would otherwise go to the object you're charging.
Things You'll Need
- a plastic comb or balloon
- A faucet (tap)water faucet [make sure the water is 1/8 inch thick]
- a sweater.
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