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,
- 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 - in thinner conductor wires electrons flow faster & there's more heat,
- electric intensity - the more amperes the more heat,
- conductor wire's material - the more resistance the more heat.
it's all not so simple outside wired circuits, however.
Source: , , Wikipedia, the Internet.