Repost from Dec.19th, 2010 (Photos from Kitchen Science Lab for Kids, Quarry Books 2014)
Have you ever gotten a shock from a doorknob after shuffling across a carpet? The term “static electricity” refers to the build-up of a positive or negative electrical charge on the surface of an object. In this case, the charged object is your body. You feel an electric shock as the charge you’ve collected from the carpet jumps from your hand to the metal doorknob.
Tiny particles called electrons have negative charges and can jump from object to object. When you rub a balloon on your hair, or a comb through it, many of these electrons are stripped from your hair and move to the balloon or comb giving it a negative charge (and often leaving your hair all positively charged and standing up as the strands try to avoid each other.)
The negatively charged balloon or comb then makes a great tool for making electrons jump around!
You can easily make a contraption called an electroscope using:
-some thin aluminum foil or mylar (the shiny stuff balloons and candy wrappers are made from)
-a balloon or comb.
- Cut the cardboard to fit over the mouth of the jar, poke the nail through the cardboard, tape on two long, thin strips of foil or mylar (see photo) and place the whole thing in the jar so the foil strips hang down, touching each other.
2. Charge your balloon or comb by rubbing it on your hair or clothing to give it a negative charge. Bring the charged object close to the nail head. You don’t even have to touch it!
What happened? Some negatively-charged electrons jump from the comb to the nail and into the strips of foil. The negative charge on the comb will push electrons (which are also negatively charged) down to the foil/mylar and give both strips a negative charge. The two strips try to move away from one another as the like charges repelled each other.
What happens when you make the strips out of different materials like paper? Are there other charged objects you can use to make your foil strips “dance”?
You can also bend a thin stream of water from the faucet by holding your charged comb next to it. The water is uncharged and is pulled toward the negative charge of the comb.
Try making small pieces of tissue paper float or dance by holding a charged comb or balloon next to them! We filled an empty soda bottle with tiny pieces of foil and made them jump around with a charged comb held close to the bottle.
Doctor Frankenstein would have loved this experiment that makes electrons jump from place to place, with a shocking conclusion. You can watch us demonstrate it on Kare11 Sunrise by clicking here.
To make an electrophorus, or charge carrier, all you need is a Styrofoam plate, a cardboard square large enough to tape the plate onto, an aluminum pie pan, a Styrofoam cup, aluminum foil and wool, like an old mitten or stocking cap.
Tape the foam cup to the inside of the pie pan. Then cover the cardboard with foil and tape the plate on to the surface, facing down.
For your Leyden jar, which can make a bigger spark and shock, you’ll need a plastic film canister or an empty spice jar*, a nail longer than the canister, aluminum foil and water.
Cover the outside of the bottom of the film canister or spice jar with foil, push the nail through the cap, fill it 3/4 up with water and replace the lid/nail so the nail is in the water. *If you’re using a spice jar, put foil on the bottom half of the jar, remove the lid, fill it 3/4 full of water, and make a new “lid” by covering the top of the container with duct tape. Stick your nail through the duct tape and your Leyden jar is ready to go! If your nail doesn’t stay in place, use more duct tape to secure it!
Now rub the foam plate with wool for about a minute. The Styrofoam attracts electrons from the wool, giving the plate a negative charge.
It’s important to do the next steps in order!
1. Put the pie tin on the foam plate. The electrons on the pie tin are repelled by the negative charge on the plate, but they can’t go anywhere.
2. Put your thumb on the foil at the bottom and leave it there while you touch the pie tin with a finger on the same hand. You should feel a small spark as the electrons jump from the pie plate to your hand, leaving the plate with a positive charge.
3. Lift the plate using the foam cup and touch it to the head of the nail on your Leyden jar. Electrons will flow from the nail to the pie plate, leaving the nail and inside of the jar with a positive charge. Repeat steps 1-3 a few times to build up a charge in your Leyden jar.
4. When you’re ready for a shock, put your thumb on the foil on the bottom of your Leyden jar, leave it there, and bring your fingertip close to the nail on the jar. Electrons will jump from the negatively charged foil on the bottom of the jar to the positively charged nail, giving you a shock. If you try it in the dark, you may see a spark as the electrons move through the air to your finger!
When you’re tired of getting shocked, you can always whip up a batch of color-changing, bubbling Magic Potion! Click here for directions and a video.
It’s been raining for about two weeks straight in Minnesota and my kids are climbing the walls. Yesterday, they built an amazing fort and played in it for an hour before they came to me asking what they could do next.
This easy experiment kept them busy for a little while.
Take a plastic comb and comb your hair a number of times, or rub it on some tissue paper. Tiny charged particles called electrons will collect on the comb and give it a negative charge.
Now, run a very thin stream of water from a faucet and hold the comb next to it without actually touching the water. What happens?
The stream of water is positively charged and is attracted to the opposite (negative) charge of the comb, pulling and bending the stream of water toward the comb.
Many more experiments to follow in the next few months! We’re planning a summer of science between our many sporting activities, so get those science notebooks ready and follow along with us!