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Ohm's Law is an example of law that doesn't actually work at all for most substances.

Interesting. I served in the military as a Precision Measuring Electronics (PMEL) Tech, and callibrated oscilloscopes and other test equipment for the guys who worked on the black boxes in fighter aircraft. I bet those fighter jocks would have felt very comfortable knowing that the entire electronics systems within their aircraft were based on mere imagination. I thought you did not believe in such things as magic.

Then you know the difference between impedance and resistance.

I thought you did not believe in such things as magic.

I don't. Most modern electronics functions because V=IxR (the common form of Ohm's Law) doesn't hold for most substances. Try taking a multimeter and measure the current running through an ordinary diode as a function of voltage and tell me if Ohm's Law holds for the diode. It doesn't. I'm sure you know that, though, and just misinterpreted the point I was making.

Interesting. I served in the military as a Precision Measuring Electronics (PMEL) Tech, and callibrated oscilloscopes and other test equipment for the guys who worked on the black boxes in fighter aircraft. I bet those fighter jocks would have felt very comfortable knowing that the entire electronics systems within their aircraft were based on mere imagination. I thought you did not believe in such things as magic.

The REAL Ohm's law reads(from Quark's FAVORITE text, Classical Electrodynamics by J.D. Jackson):

J = s E

(Note: the 's' should be a greek 'sigma' character, and may actually appear as such in your browser. It's not working for me for some reason.) Where J is the current density, s is the area through which the current is moving, and E is tha applied electric field. It so happens that this rather evil little equation reduces to the simple V = IR that everybody knows and loves for most metals. So pretty much everything YOU had to manipulate in your career as an electrician followed the more practical version of ohm's law. Here's a website that explains the microscopic view of Ohm's law in more detail:

http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmmic.html#c1