Fun with Less Kilowatts — Build the Electroscope

By Vernon Trollinger, July 19, 2017, Family

Static electricity can lurk anywhere in your home. You can find it by building your own electroscope.

Welcome to Fun with Less Kilowatts! We believe that science experiments at home can be a creative way to engage kids in learning while having fun. They can be educational AND great activities to keep your kids busy and away from the television. Each month, we’ll feature a new science experiment that can be a great resource for parents and teachers.

Building the Electroscope

The other day, I was going to do some work on my roof and I needed a small plastic bucket. Now, I had an ice cream bucket that was just the right size but there were some flakes of old latex paint peeling from the inside. So, I got a rag and began rubbing the peeling paint off the inside of the bucket. I didn’t use any water. All I had to do was use the rag to scour out the bucket

I had the bucket tucked into the crook of my right arm. I took the rag and began scouring it out with a circular motion, going round and round the inside of the bucket. Each time, the rag got close to my arm, the hairs on my arm would stand up and track the rag as it moved past and then lie down again.

IT FELT AND LOOKED REALLY WEIRD!

Of course, I didn’t completely wig-out because I knew what was happening. I was creating an electrostatic charge on the rag by rubbing it against the side of the plastic bucket and the charge attracted my arm hairs. It’s the same thing that happens when you rub a balloon on your head. You pull the balloon away and your hair is attracted to the balloon.

But not everything that has an electrostatic charge will get your hair standing up. If you’re curious to see just how many things build up an electrostatic charge, you can build a foil leaf electroscope.

The first foil leaf electroscope was built in the 1780s by Abraham Bennet, a clergyman who dabbled in science and became a member of the Royal Society. Over time, the materials have changed some, especially the substitution of aluminum foil for the gold foil, but it still basically does the same job.


The Materials

  • A plastic jar or bottle with a plastic lid.
  • About 6 inches of 14 to 18 gauge copper wire.
  • 3 inch by 1/2 inch piece of aluminum foil
  • A balloon. (We used a nice red one.)
  • A nice dry location on a dry day.

The Directions

  1. Drill a small hole in the lid just a little smaller than the diameter of your wire.
  2. Push one end of the wire through the hole and form that end into a flat bottom hook.
  3. Twist the other end into a spiral or coil.
  4. Cut a strip of aluminum foil and gently fold it in half, careful not to crease it.
  5. Drape the strip over the flat bottom hook.
  6. Put the flat hook end with the strip into your container and close it up.
  7. Blow up a balloon and rub it against your hair.
  8. Move the balloon to towards but do not touch the wire spiral. Watch what the strip does.

The Result


The ends of the aluminum strip move away from each other!

The Science

The copper wire and aluminum strip exist in a balanced state with an equal positive and negative charge. Different materials, however, can easily take on positive or negative charges just by rubbing them against something, such as when you rub a balloon against your hair. The balloon will take on a negative charge.

Static electricity is an imbalance of charge that does not change (hence, “static”) until something comes along to drain the charge. The negative charged balloon is used to “unbalance” the charge in the electroscope. When you bring the balloon towards the electroscope’s coil, it attracts the positive charges to the coil.

Meanwhile, the negative charges stay at the other end. Since there are now like charges in the ends of the strip, that causes the strip ends to repel each other.

More Than Just Static

Static electricity isn’t a trivial form of electricity. It’s actually a high voltage. Your body is capable of generating a HIGH voltage static electric charge that starts being noticeable at around 500 volts. If you’ve ever gotten a shock from a door knob and see the spark jump from your hand to the knob before you touch it, you’re delivering a charge up to 7,000 volts! Static charges can be made to go even higher as this shocking, hair-raising Myth Buster’s video shows.

Do you have any fun and kid-friendly science experiments you’d like to see us try for Fun with Less Kilowatts? Share with us in the comments!

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About 

A native of Wyomissing Hills, PA, Vernon Trollinger studied writing and film at the University of Iowa, later earning his MA in writing there as well. Following a decade of digging in CRM archaeology, he now writes about green energy technology, home energy efficiency, DIY projects, the natural gas industry, and the electrical grid.

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