March 14, 2005

TV Zapping

Back a few weeks ago when I was home because the campus was closed (snow) and I was recovering from the flu. I decided to do a little science experiment with the kids.

I chose one of the experiments listed on the Science Toys page that appeared in a Shotgun post a while back.The experiment involved building your own Franklin Bells out of soda cans. “Franklin Bells” are two bells with a light clapper hanging beneath them. Static electricity buildup causes the clapper to fly toward one of the bells until it contacts, and then it flies back.

I ended up modifying the activity, but a good time was had by all. Continue reading for pictures and a video of the outcome.

The TV is covered in foilThe static electricity is provided by the television set. When the TV is turned on or off, a charge accumulates on the surface of the TV screen. This charge can be gathered by placing a large sheet of aluminum foil over the screen. (see the image — click for larger) Once harnessed, the electricity could be used to charge up one of the Franklin bells, which is supposed to cause the clapper to fly from one bell to the other, making noise and amazing everyone! First the clapper is attracted to the newly charged can, then (as it acquires charge from touching) it is repelled. It hits the other can, discharges, and repeats until the charges are not strong enough to move the clapper.

Well, it worked. The clapper did fly back and forth. The girls thought it was neat. I described some facts about static electricity. But we noticed other things. The foil would move a lot when the TV was turned on or off. And we would get zapped a little bit (it stung) if we touched the can during the experiment.

I was amazed that you could harvest so much static electricity off the TV screen. But I was even more “shocked” when I was holding a grounded wire and brushed the can by mistake. Once I was better grounded, the shock was enough to make my hand go a little numb. That’s a pretty good amount of voltage. It occurred to me that we ought to be able to see that much voltage jump a gap through the air.

First, we set up a stiff wire near a hanging piece of aluminum foil. Similar to the Franklin bell, the plan here was to have the very light foil move when the wire got charged up. The difference in charge would attract the foil. But when the foil got close enough, we hoped to see (and hear) the circuit complete as the electricity jumped the gap.

It worked!

But all that movement was getting in the way of actually seeing the spark fly. So I rigged 2 wires. One was connected to the TV foil, the other was grounded. This time I could adjust the gap and keep it stable. After some experimentation, I found a decent gap distance (it was a little over a centimeter).

A forked sparkFinally, we were able to get some pretty dramatic sparks captured on film, and very loud zaps!

As you can see here, we even got some sparks that forked like lightning. The larger image is even more impressive.

I’ve made a small video of the experiment which you can check out in the links at the end of this entry.

Its important to point out to children that, while playing with low powered static electricity is fun, you can get zapped a little bit (the kids both wanted to feel what it was like, and got very small zaps). But high-powered AC wall voltage is an entirely different ballgame. Children (and all people) need to understand that you playing with wall current can be very dangerous. I blew up a wall socket and a toy as a kid once because I was playing with the household electricity. I was lucky I wasn’t hurt, and it sure made me respect the stuff.

While electricity can be dangerous, it’s also a heck of a lot of fun, and it’s fun to get familiar with what you can safely do with it.


  • Static Electricity TV Zapping - The Movie! (hosted at The video is about 1.2 MB.
  • Check out my Experiments photo gallery to see all the pictures from this experiment in one place. All the photos from this experiment are dates Feb 25, 2005. Notice the last image in the series — there are a bunch of colorful artefacts in the video signal. I am guessing that the spark caused some kind of electromagnetic interference that momentarily messed up the CCD of the camera. I was holding it pretty close.

Details on the video:

I used the free Windows Movie Maker (Windows XP’s answer to iMovie) and, predictably, they only support Windows Media Player format as an output method. I’ve got to get my laptop fixed, or get better video software for the PC.

For those interested, Windows Movie Maker is halfway decent for making quick movies. It’s quite a bit better than some pay software I’ve used if your needs are simple and you want something done fast. But the lack of ability to save to other codecs (especially Quicktime codecs) is just nasty. It may be a proprietary thing on Apple’s part. The best Apple codecs are not open formats. However, Movie Maker doesn’t give you much choice at all.

Posted by James at March 14, 2005 7:45 AM
Create Social Bookmark Links

I'm thinking of a way to hook this up to my pets to zap them when they're bad.

Posted by: Patti M. at March 14, 2005 12:09 PM

Science is cool!

Posted by: Chuck S. at March 14, 2005 12:42 PM

Yes, and William Petersen makes scientists look sexy, which is a refreshing change from how scientists are usually portreyed. He's hot.

I, myself, am married to a sexy scientist!

Posted by: Patti M. at March 14, 2005 12:46 PM

That sounds like it should be aon a T-Shirt.

"Married to a sexy scientist."


"He blinded me with science!"

Of course, that has different implications for those scientists who work with lasers.

Posted by: James at March 14, 2005 12:54 PM

Hmm...I like it!

"Married to a sexy scientist"

How about "Science is sexy. Ask me how I know."

Nah, too many weirdos on the T would ask.

Posted by: Patti M. at March 14, 2005 1:00 PM

Yeah. I think if you wear a shirt that has the word "sexy" on it, the T weirdos will tune out any other context and try to paw at you.

Posted by: briwei at March 14, 2005 1:43 PM

Good point, Bri. In fact, my post originally employed "paw," but I changed my mind.

'Tis true. Weirdos on the T are to be considered. Can't wait for Thursday (red hair + St. Patrick's Day = comments from T patrons).

If I had a nickel for every time some geezer said to me "With that red hair, you must be Irish!" I'd have lots of nickels.

Oh, joy. St. Patrick's day in Boston, when everyone thinks a) they're Irish and b) this day is an excuse to drink green beer and act like an ass.

Posted by: Patti M. at March 14, 2005 1:58 PM

My sister's birthday is St. Patti's day. So, my grandfather used to make her a green rye bread at the bakery. The intersting side effect was that the green food coloring would bleed onto the turkey in the sandwich and people would think you were eating moldy food.

Posted by: briwei at March 14, 2005 2:34 PM

Patti Wrote:
"Oh, joy. St. Patrick's day in Boston, when everyone thinks a) they're Irish and b) this day is an excuse to drink green beer and act like an ass."

As opposed to every other day when (almost) everyone just acts like an ass ;)

Posted by: Jay at March 15, 2005 10:03 AM

Good point, Jay, but here's the diff: I have red hair, and on St. Patrick's day, these ass-like people feel compelled to touch/speak to/interact with me because "with red hair like that, you must be Irish!"

Go away, ass--you are not worthy of my time. And you smell like stale beer.

Posted by: Patti M. at March 15, 2005 10:46 AM

congrats mate! Fine job and fine site!

Posted by: at July 2, 2005 4:40 PM

Copyright © 1999-2007 James P. Burke. All Rights Reserved