What is voltage? Text books give a non-answer; something to do with electromotive force. Fuck off. I mean please explain to me what's going on with voltage. What is it and what are it's properties in physics. The fact that we don't have an easy time answering this question leads me to believe we have rather poor understandings of inductance and capacitance too. But that has been the subject of other posts.
Voltage is always given as a potential difference. There is always a system with some amount of energy that will be compared to produce a potential difference. I'll repeat my question: what is this energy difference? What causes it? Let's start with the units. Volts are Joules per Coulomb. This means that six times ten to the power of eighteen electrons in two different places will have an energy difference of one Joule. But what causes this energy difference?
I know all these questions are annoying but it annoys me even more that we can't just pick quick answers off of Wikipedia. Shouldn't Stanford and the DoE's X-Ray lab be looking at this stuff? Let's describe what we do understand. Voltage has been related to tension and pressure in the past as analogies. Those analogies may or may not hold. I'm not as interested in analogies as I am in the physical truth.
Previous posts have shown electric generators to whip electrons onto a return wire sucking electrons from the hot wire creating what we call positive charge. There is now a deficit of electrons on the hot wire that is being back-filled by the load. Electrons move at about 1% the speed of light so they can back-fill fast but they tend not to. The drift velocity of an electric circuit is almost always radically lower than the root mean squared velocity of the electron. So an electron surplus or deficit may contribute to a negative or positive voltage respectively.
That may not be all that is going on. I'll leave out parasitics related to the telegrapher's equations. What about the root mean squared speed of the hot side of the circuit related to the root mean squared speed of the electrons on the return side of the circuit. These quantities are hard to measure. Electrons move quickly and I'm not aware of any laboratories working on characterizing them.
Finally, a contributor to voltage may be hot carriers. Very few, fast moving electrons that can devastate transistors and provide a visible spark show.
Scientists studying the upper atmosphere talk about density and temperature of charge to characterize particles. That helps us only a bit with the characteristics of low voltage and high voltage electric circuits here on Earth.
A deficit or surplus of electrons relative to the nuclei in wires may cause an electric voltage relative to other wires. The root mean squared speed of electrons as it differs from another point in a circuit may cause a voltage. The drift velocity may be a measure that correlates to voltage. Hot carriers may also be a cause of voltage.
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