Floating Static Bands
Using a little static electricity and some practice, you'll cause objects to float in midair.
By doing this research, you could end up in the company of people like Ben Franklin, James Watt, Thomas Edison, and Nikola Tesla. Then there are the people behind LEDs, button batteries, and neodymium magnets who started out as innocently curious about electricity as you are now. You’re headed for amazing discoveries involving both stationary and moving electrons.
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- Lightweight, plastic grocery bag
- PVC pipe, 1" (25 mm) diameter, 3' (1 m) long
- A piece of fur or wool cloth
- Pencil (or dowel), Tape, Scissors
- Other items as needed (See the "Take It Further" section.)
- Adult supervision
Securely tape the wooden dowel (or pencil) to an end of the PVC pipe. The pencil should extend beyond the pipe by about 5″ (127 mm).
NOTE: It’s important to keep the pipe and the dowel electrically separate. Using a 1-inch stopper in the end of the pipe to hold the dowel is ideal but securely taping the dowel to the end of the pipe should be fine, too.
First, cut the handles off of the bag. Next, cut a ring of plastic from around the opening of the bag that’s about 1″ (25 mm) wide. You need a lightweight, continuous band for this activity.
Place the band in the the fur and rub the fur vigorously all over it to build up a static (not moving) charge in the band. You may hear crackling as the charge builds. Place the “charged” band on the table.
Snugly hold the the same fur against the PVC pipe and vigorously rub the fur along the pipe’s length to build up a matching static charge. You may hear crackling again.
This step is a little tricky and may take some practice. Don’t give up because you’ll be amazed at what happens! Hold the pipe by its non-pencil end and use the tip of the pencil to lift the band. With a gentle flick, toss the band straight up into the air. Then, immediately position the pipe underneath the band at the height of the band’s rise to cause the band to mysteriously float in the air. You can even walk around the room and the band stays suspended in midair above your “magic wand” — well, OK, above the charged pipe, anyway.
How Does It Work
The word “static” means stationary, little or no change, or not moving, e.g. “A static display doesn’t move.” So, static electricity is an electrical charge that’s not moving; it invisibly builds up in one place such as on the surfaces of the band or on the PVC pipe. You “see” it by what it does to the objects that hold it or come near it.
Static electricity is governed by charges on particles: they’re either positive protons (+) or negative electrons (–). Similar charges (+ and +) or (– and –) repel or push away from each other. Opposite charges (+ and –) attract or pull toward each other. With that little bit of information, you can probably explain what you saw happening to the band.
Rubbing the fur against the band as well as the PVC pipe transfers a negative charge to both objects. The band floats above the pipe because the increased negative charge in both objects causes them to repel each other. If you really want to impress someone, just tell them that it’s a demonstration of “electrostatic propulsion and the repulsion of like charge.” Wow – that should do it.
Take It Further
- When you do this next activity, make sure your hair has been washed and is completely dry. It helps if there’s low humidity (air moisture), too. Blow up a 10″ (25 cm) balloon and tie it off. (Be sure to test other sizes and types of balloons, also.) In front of a mirror, rub one side of the balloon briskly and firmly all over your clean, dry hair several times. The charge piles up on the side of the balloon near your hair. Hold it away from your head and look for a hair raising result! Sometimes you can press the now charged balloon onto the wall and the attractive charge holds it in place. From what you know about static charges, you can likely explain what’s happening. Use a clean, dry comb in your hair instead of a balloon and see if you can generate a charge. If you hear popping and snaps, you did it! When you rub a balloon on dry hair, the balloon picks up electrons, making it negatively charged and leaving the hair positively charged. Since the hairs have the same charge, they want to get away from each other so you see them spreading out. But because opposite charges attract, bringing the balloon near the hair causes the hairs to cling to it.
- Charge a balloon (as you just did) and hold it close to a Ping-Pong® ball sitting on a table. The ball will start to move toward the balloon. Keep the balloon ahead of the ball and pull the ball over the table top using only attractive electrical charges.
- Charge a balloon and then blow soap bubbles. Bring the balloon close to the bubbles and they move rapidly toward the balloon. Tease the bubbles around the room with the balloon.
- This may be the hardest thing you’ve ever done! Rinse a 1-liter bottle and its cap and let both dry completely inside and out. Fill the bottle with a quarter cup of Styrofoam beads, 1/8″ (3 mm) diameter, and seal the bottle with a cap. NOTE: The beads will not cooperate and will go everywhere but into the bottle. When more than a few have made it, cap the bottle. Rub the bottle on your head (or better yet, your friend’s head) or on a wool sweater. Observe the effects of static electricity on the beads. Simply run your hand over the plastic bottle and build up a static charge. Watch the static beads inside jump from side to side to stay away from your finger. Set the bottle upside down on a table and bring a finger close to but not touching it. How do the beads react to your finger even though you’re not touching them? You could call them “scaredy beads” because they move quickly away from your finger but, c’mon, they’re only little white beads! The beads clearly had the same charge as your finger and were repelled by it. Some beads in the group had the opposite charge as your finger and were attracted by it. That’s why other beads move out of their way: they share the same charge. Also, the beads clinging to the plastic had the opposite charge from the plastic. That’s why they stuck to it.
- What about tiny pieces of paper confetti? Use the scissors to make some and then bring a charged balloon near them. The paper isn’t charged so you might expect nothing to happen. But, the paper is attracted to the balloon. The negative charge on the balloon repels the electrons in molecules of the paper. This makes them (on average) move away from the balloon’s charge which enhances the positive charges in the paper. Because electrical forces decrease in strength with distance, the attraction between opposite charges is stronger than the repulsion between similar charges. This leads to an overall attraction. The paper is said to have an induced charge. This also applies to a charged balloon sticking to a wall and a charged balloon attracting other “uncharged” objects.
Science Fair Connection
A Floating Static Band is a pretty cool activity but it’s not a science fair project. You create a science fair project by identifying and testing variables. A variable is something that might change the outcome. Consider some of the variable options you might test and write up for a science fair project.
- You know what happens when you rub fur or wool on the PVC pipe. Use a different material but keep everything else the same. How does it change the results. Test cotton, silk, polyester, or even a stuffed animal.
- Change the material used in the floating object. A thin packing foam might work so redo the test using paper, aluminum foil, wax paper, plastic wrap, a sticky note, poster board, newspaper, etc.
- Since you’ve seen what happens to beads in a plastic bottle when they are exposed to a static charge, use a glass bottle instead. What results do you get when you rub the glass bottle on your hair or on a wool sweater?
These are just a few ideas and you certainly aren’t limited to them! Come up with your own variable to test. Remember, you can change only one variable for each test while making sure that all the other factors in your test remain the same.
This activity was developed by Steve’s good friend and fellow science teacher, Bruce Yeany. He uses it to teach “electrostatic propulsion and the repulsion of like charge” to his very lucky students.