What carries the energy in an electric current?

[scoobmx]

Imagine you put a table inside a big solenoid. On that table you place a magnet and put a heavy object on top to make sure the magnet can only move slowly.
Then you turn on the solenoid so that the magnet moves slowly over the table at a !constant! speed.
Because of friction, the table and the magnet will become warmer. You could claim that the kinetic energy of the magnet was converted to heat. But you could also say that the energy of the field was converted to heat in a relatively direct manner.

Yes but the question was what carries the energy in current. The part lost to resistance is no longer part of the current.

 

[DrZoidberg]

I guess that means the part lost in the device you are running is also no longer part of the current?
You don't lose current in a resistor. The current stays the same, what you loose is potential.

 

[sophiecentaur]

The electric and magnetic fields carry the energy, but the movement of electrons is influenced by these fields. I have always thought of the kinetic energy of the electrons as mechanical energy, that become heat when they scatter on impurities (the phenomenon of resistance).

Have you not read all the preceding posts that tell you the amount of KE carried by electrons is as near zero as makes no difference? Resistive wire can get pretty hot. Where would the energy come from if it relied on electron KE?

You could prove this for yourself if you work out the actual mass of all the conduction electrons in a wire and then multiply it by v²/2 , with mean v = 1mm/s.

 

[scoobmx]

Have you not read all the preceding posts that tell you the amount of KE carried by electrons is as near zero as makes no difference? Resistive wire can get pretty hot. Where would the energy come from if it relied on electron KE?

You could prove this for yourself if you work out the actual mass of all the conduction electrons in a wire and then multiply it by v²/2 , with mean v = 1mm/s.

That 1 mm / s is the drift velocity, not the actual velocity. Even at 0 drift velocity electrons have kinetic energy that approximately follows the equipartition theorem (hence 'electron gas').

If truly electrons carried the energy in the circuit then when you flip a light switch you would have to wait for the 1 mm / s electrons to crawl to the light bulb. But we all know it's nearly instantaneous. It's the electromagnetic field that conveys the energy.

 

[sophiecentaur]

That 1 mm / s is the drift velocity, not the actual velocity. Even at 0 drift velocity electrons have kinetic energy that approximately follows the equipartition theorem (hence 'electron gas').

If truly electrons carried the energy in the circuit then when you flip a light switch you would have to wait for the 1 mm / s electrons to crawl to the light bulb. But we all know it's nearly instantaneous. It's the electromagnetic field that conveys the energy.

I thought we'd been there before / knew that. That post of mine that you are quoting is a (several times) repeated reply which tried to knock the electron KE idea on the head. It was just a suggestion to try it out for himself.