Obvious to everyone but Dave. Pressing a spring by expansion then releasing it by unexpanding doesn't really do any work, it just temporarily stores some energy.
He'll never get it though. He still thinks a resistor turning electricity to heat is imposible.
NT
Of course in the spring case some of the energy is lost as heat, but in the heater case none need be lost as mechanical work.
heat is mechanical work done on molecules
So you can press a spring in your little world with no energy involved?
And if it released an equal amount of energy on release, you'd have the perfect energy storage solution.
Do you ever think before posting?
I'll say again. Nothing in this world is 100% efficient. Of course you can approach it with some things. But never achieve it.
Why do you think that nothing is 100% efficient? The only reason for believing this that I know of is a a thermodynamic one, and this does not apply ot heat production as an endpoint. Though it certainly would apply to heat *transfer*, but we are not talking about this.
Of course we are. Transferring heat from an element or water or oil or whatever.
FWIW springs return the energy when released. But a hot radiator is not a compressed spring.
perfect? you dream
NT
You're a dummy.
His thinking difficulty is not afaik thermodynamic in nature.
Anything with 100% efficiency is your dream.
Thermodynamics does not forbid 100% efficiency in the conversion /to/ heat. That does not mean it is easy to achieve /in practice/.
Rather a lot of texts (used to) state that 100% efficiency is /easy/ to achieve. A common example they gave is a person pushing a box across a flat floor at a constant speed. All the work is (they say) converted into heat in the box/floor system. One of my undergraduate tutorial tasks was to discuss that and some similar statements. My recollection is points included:
where's the pressure suit to limit heat to that system alone (and even then no vacuum is perfect)?
where are the insulated mittens if it's not the box/floor/person system?
what are the materials of the box and floor to guarantee there are no endothermic reactions?
ditto as regards energy stored in defects in crystalline structures?
A better example IMO are the evolutions of Joule's paddle wheel experiment - though even there I would question 100% conversion.
resistors do a fine job of it, if not overloaded. Wouldn't surprise me if there were a trillion of them out there.
NT
My physics is well past its 40th anniversary of disuse so please remind me how you have an electric current passing through as resistor with /zero/ radiation and particle emission (taking account also of quantum tunnelling). Please bear in mind that (1 - 10^-99) ain't 100%.
Radiated heat is still heat. I'm not sure if that's what you meant.
What sort of particle emission do you expect from a 0.2W resistor running cool at 5v drop?
NT
Have something to add? Share your thoughts — no account required.
Ask the community — no account required