is this true? thanks for help. i wished to abstract (generalize on topic) from electric current in physical wires, to for example in air. i hope this is in proper forum section. ---- Electric current's density J depends on electric current's intensity I measured in (A) & on conductor wire's gauge S measured in mm2. It is described by a physical formula: J = I / S, where: - J is electric current's density, measured in A / mm2, - I is electric current's intensity, measured in A, - S is conductor wire's gauge, measured in mm2. As electrons flow between two points with different electric potential (amount of electrons & positrons in an atom), physical medium resists their flow & gets heated. Amount of heat depends on: - conductor wire's gauge, measured in mm2 - the more matter the less heat, - electric intensity - the more amperes the more heat, - conductor wire's material - the more resistance the more heat. in thinner conductor wires, electrons flow faster.