On Tue, May 7, 2024 at 05:12 PM, Dale H. Cook wrote:
On 5/7/2024 4:43 PM, cheater cheater wrote:
also why buy aluminium leaf? why not use alu foil?
Aluminum foil is far too thick. An electroscope needs minimum mass, and that
means leaf, not foil. The repulsive force in an electroscope is far too low
for foil to work.
I believe it's the stiffness, more than the mass, that's important, but the problem remains that the electroscope needs to be sensitive to extremely small forces.
For detecting direction of current flow you want a sensitive galvanometer, of
the type used as a detector for instruments such as a Leeds & Northrop Type
K-3 Universal Potentiometer. You would probably need an adjustable current
limiter of fairly high resistance to avoid damaging the galvo.
A galvanometer will tell you the direction of current flow, but it won't tell you which side got the built-up charge. He might be able to discern this by taking an electroscope around the store and touching it to various things, the cart: his finger, something "grounded." It should be possible to eventually pick out which item is different. Even this may be difficult, because I'm not sure what effect charge on the electroscope housing may have. It might be necessary to ground the housing with a wire that's long enough reach "ground" and also allow the electroscope to move around to reach everything he wants to check. (The problem here is that electroscopes traditionally have two glass windows, so the interior is not a completely field free region.)
--
Jim Adney
Madison, WI USA
