Alright already. I thought every good Day Trader knew these laws:
Ohm discovered the fundamental law of the electric circuits by analogy with the phenomenon of the propagation of the heat by conduction.
As the heat flux Q/t = KS (T1-T2)/L (calories/second) goes across a layer of a conducting material with the lenght L, between whose sides, having the section S,exists a given difference of temperature T1-T2 , with T1>T2 , so the electric current intensity I = Q/t (that is the ratio electric charge/second) that goes across a conducting wire, with the lenght L and the section S, is directly proportional to the potential difference V1-V2 applied to the extremes of the wire:
I = k S (V1 - V2)/L, where k is a constant (the so-called specific conductivity), depending on the conducting material.
The electric current I is directed, by convention, as the thermal one, from the points at a greater potential (V1) toward the ones at a lower potential (V2).
In fact, although is still operating this convention, established before the discovery of electron, however we know that the effective direction of the current in an electric conductor is the same as the one of electrons, that,by means of their negative electric charge,are moving from the points at a lower potential toward the ones at a greater potential.
If we rewrite Ohm's law as V1 - V2 = I [L/(Sk)] = I R, the constant
R = L/(Sk), called resistance, evidences the direct proportionality between I and V1 - V2 , and is directly proportional to the lenght L of the conducting wire ed inversely proportional to its section S.
