# Triboelectric effect and measuring charge

• August 10th, 2007, 05:52 AM
pubson
Triboelectric effect and measuring charge
Hi

Im a student who is doing a project which in part requires the use of the triboelectric effect to charge up dust and then look at the effects of this dust when it comes into contact with a low frequency antenna.

I didnt study this at school so all I have to go by is the wikipedia page on the subject, my tutor want to measure the polarity and the amount of charge on a rubber balloon when it is rubbed against various materials (eg wool and polyester.) Does anyone here know how to measure the polarity and/or strength of charge on a triboelectrically charged balloon?

Also Iv assumed that simply putting the dust or sand into contact with the charged balloon will in turn charge the sand, is this correct?

Thanks in advance for the help!
• August 10th, 2007, 04:05 PM
SteveF
You can determine the polarity of the charge by separately rubbing fur with rubber (or any other combination) to place a positive charge on one substance and negative on the other. See the Wiki page at http://en.wikipedia.org/wiki/Triboelectric_effect. Then see how your balloon behaves as each item approaches.

To measure the amount of charge, I recall a college lab project in which we used some instrument called a ballistics galvanometer. I doubt if you can find one, but check with your tutor. Maybe he is hoping you would ask. See the Wiki article at Â*http://en.wikipedia.org/wiki/Electric_charge.
• August 15th, 2007, 05:26 AM
talanum1
Charge
:)

The charged baloon creates a static electric field. This affects a capacitor held close by it by a tiny amount. The capacitor will behave slightly different than usually.
• August 15th, 2007, 06:35 AM
SteveF
What instrument would one use to measure the changes in the capacitor?

That is, can this experiment be performed by the amateur?
• August 16th, 2007, 07:52 AM
talanum1
Charge measuring
:P

You can use a static electric voltmeter as an alternative.

The effect on the capacitor may be too tiny to measure. It would require an alternating current source and voltmeter, together with some mathematics, not so complicated.
• August 16th, 2007, 07:55 AM
SteveF
Â*Then why not use the static electric voltmeter directly on the balloon?
• August 16th, 2007, 08:15 AM
talanum1
:-D

You can try the voltmeter.

There is another device that allows you to detect a charge, (not measure it). I forgot the name but it is a metal box with electrode on top and a glass side with a rod inside and a gold leaf attached to it.
• August 16th, 2007, 09:23 AM
Old Geezer
Quote:

Originally Posted by talanum1
:-D

You can try the voltmeter.

There is another device that allows you to detect a charge, (not measure it). I forgot the name but it is a metal box with electrode on top and a glass side with a rod inside and a gold leaf attached to it.

That's basically a Leyden Jar. And it actually will measure the amount of charge to a degree by the distance of the separation of the leaves. The greater the separation (wider the angle) the greater the charge.
• August 16th, 2007, 09:44 AM
SteveF
Â*
No, a Leyden jar is merely a primitive capacitor.

The instrument with the gold leaves is called an electroscope.

But there are simpler and more effective devices to detect and measure charge.

http://amasci.com/emotor/voltmeas.html.
Â*
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• August 16th, 2007, 09:59 AM
Old Geezer
Quote:

Originally Posted by SteveF
Â*
No, a Leyden jar is merely a primitive capacitor.

The instrument with the gold leaves is called an electroscope.

But there are simpler and more effective devices to detect and measure charge.