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Q & A: charging glass via friction

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Most recent answer: 05/28/2019
Q:
Hi, I worked for several years as a science teacher in a school, and have been interested in trying to re-create experiments from the past. I've been especially interested in electrostatics and have had some success in replicating some historical experiments, including making a friction-type generator from a plastic container.One of the things that has struck me is my total failure to charge glass by rubbing with silk or other materials. Glass seems to be a ubiquitous material in historical treatises on electrostatics, and I've been totally surprised by my failure to charge it even slightly. I've been searching for an answer for a long time, but haven't had any luck. I'm hoping that somebody at this dept would be able to enlighten me. Is it that the glass which used to be made in the 18th and 19th centuries are different from the glass made now, or something else?
- Kishore Athrasseri (age 30)
Bangalore, Karnataka, India
A:

We have a lecture demonstration here in whch we can charge a glass rod by rubbing it with fur or other things. So it does work. I don't think that modern glass is different from older glass in a way that's important for this effect. One thing that makes a big difference is atmospheric humidity. We have better luck on very dry days, just as accidental static electricity is a bigger problem on those days. Bangalore is often very humid. Is there a dehumidified room you could use? Otherwise, perhaps trying in a drier month (March?) might help.

Mike W.


(published on 05/28/2019)

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