“bg, I’m surprised. Will you please elaborate?”
When current flows through a material, with direct current it flows through the entire material. So if you had a plated coin, the outside material would have a resistivity and the inside would have a different resistivity.
ie; resistors in parallel. The equation is R total = R1 (times) R2, (divided by) R1 plus R2
Understood.
I didn’t think of parallel resistors because of the “envelope” configuration.
Thank you very much!
“resistors in parallel. The equation is R total = R1 (times) R2, (divided by) R1 plus R2”
Yes, that is true, but if you have a fair thickness of gold, it becomes a much less simple matter to determine that the deviance of increasingly small variances is due to the bimetallic nature rather than some other test artifact.
As example, consider a plate of gold a sixteenth of an inch thick, and an inch by an inch! With a similar gold section a quarter inch high folded up on each end as the contacts. This will have very low resistance. Now weld a plate of tungsten on top. While that adds to conductivity per the cited equation, at that point things like shape (minute transmission distance differences) and contact become important.
You’d be better off detecting other properties, like using sound or some other vibration-based tech like a penetrating EM field to detect the interfaces between conductivities, densities, or internal reflectivity.
I suppose if you had lab-grade equipment with really high amperages, and a standard for shapes, and contact points it might work...until someone put a little silver on the tungsten.
Just so we’re clear...I agree you are correct in an ideal sense.