Invictos - 14-7-2016 at 11:50
Good Afternoon everyone,
I have a few questions regarding Leyden jars which I cannot for the life of me figure out, and I figured y'all would be the ones to ask (Long time
reader, first time poster)
I know leyden jars increase in voltage the more they're charged, however, assuming it exists, how can one calculate the upper limit of this voltage?
If you can't (which is understandable, there are hundreds of ways to make a leyden jar), what techniques can you use to measure the voltage in that
high a range?
There are tons of ways to measure capacitance, but I can't find anything for voltage
Thanks in advance,
Invictos
Sulaiman - 14-7-2016 at 12:20
The only simple' method of measuring the voltage would be to use a variable spark gap
e.g. http://www.hindawi.com/journals/aee/2014/980913/
Artemus Gordon - 14-7-2016 at 16:21
Leyden jars are capacitors, and in theory the voltage across them could be essentially infinite. More voltage would just cram more charge in. But of
course in the real world, there are real limits. The insulating material between the plates has a breakdown voltage, where it can no longer keep the
charges separate. This differs for different materials, and porosity and density differences in the material can cause weak spots. Also, even if you
use a good insulator like thick glass, the air surrounding your jar might provide a current path at a lower voltage than the glass would. I don't
think it is possible to calculate the true breakdown voltage. The best you could do is try to look up a breakdown voltage for the insulator and reduce
it with a really big safety factor.
[Edited on 15-7-2016 by Artemus Gordon]
Morgan - 14-7-2016 at 18:34
One time out of curiousity I picked a grapefruit off my tree and set it on a sheet of telfon and charged it up using a piece of gray PVC and paper
towel. Under the teflon was a metal jar for ground. The spark jumped over to a pole with a small ball bearing which teases the spark but not so much
as to constantly bleed the charge away. Sharp points will do that.
Anyway, it would be a funny project to calculate the capacitance and breakdown voltage of a grapefruit/telfon arrangement. It's interesting too how
those acrylic blocks can be charged up/hold a charge like a capacitor when making Litchtenberg figures.
Sometimes when charging I noticed arcing little pops and sparks on the surface of the teflon, little discharges not associated with the actual object
I was charging so to speak.
https://www.youtube.com/watch?v=P-NbshIOJmc
Where the charger idea came from.
http://amasci.com/static/foster1.html
[Edited on 15-7-2016 by Morgan]