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What should I expect to see from my Leydens jar? Answered

My son has built 3 different Leyden's jars for a science fair. None seem to spark. The foil is very smooth( it looks like it was painted on) There are no holes. I've tried different chains. I've tried glass jars, as well as plastic. We are trying to charge to jar by rubbing a balloon on our heads and touching the metal ball on top. We hear a "pop" but never see a spark. We've continued this up to 100 times, and still no spark from the wire which touches the outside foil, and points to the metal ball on the lid. I'm definately no scientist! Do you have any ideas? I've tried holding the jar while charging it, as well as sitting it down, and I still get no results. The closest thing I've gotten was the balloon appeared to act like a magnet; it pulled the plastic jar closer when the balloon had static on it. Thank You, Jodie


Mr. Apol

Best Answer 9 years ago

You've got a charge, it's just very small. For a visible spark, you need a stronger charge. Take a length of half-inch PVC pipe about 3 feet long. In your left hand hold a nice scratchy wool scarf. With your right hand, rub the pipe back and forth through the scarf. Grip it fairly tightly, but keep your left hand still and do all the pushing and pulling with your right. Now, practice keeping the part of the pipe that emerges from the scarf close to the top terminal of your jar. It doesn't have to touch. You should hear distinct crackling as the charge passes from the pipe to the jar. You may see sparks in low light. Give the Leyden jar 50 strokes of the pipe and try discharging. I think you'll see noticeable sparks then.

Alternately, you can hold the top terminal of the jar close to a CRT or TV screen. Static electricity will collect in the jar, albeit somewhat slowly.

A problem you may be having is grounding. Do your Leyden jars have good ground contact? The metal lining on the outside of the jar must come into contact with something grounded--a metal stove top, a steel sink, etc. Without a good ground connection you can't accumulate much charge.

Try this site for more hints: http://www.alaska.net/~natnkell/electrophorus.htm

Let us know if these suggestions help!


Mr. Apol, You did it!!! I bought the PVC pipe and followed your instructions...and I finally got a spark! My 6th grader is so excited to give his science fair presentation now. Thank you so much for your help. Jodie

Great! Building Leyden jars is how I got started with electricity as a hobby. Good luck.. Paul

You are getting a spark, that's the "pop" - it's just too small to see (try doing it in the dark?).

Use a higher-voltage supply to charge it - if you can't get an actual electrostatic generator, use the screen of a cathode ray tube (non-LCD TV or computer monitor) as you switch it on and off.

There are many instructables showing how to make a Leydens jar, you could use them for trouble shooting reference, if that doesn't work then I suggest that you try a more powerful power supply such as a Wimshurst Machine.