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I understand that the laws of physics (as we know them) cannot be violated, but what I would like to know is what I'm missing, because I know there is some explanation that I'm not accounting for.

Imagine we had a room temperature superconducting material (no energy needs to be expended in cooling it to the point of superconductivity). We could then create a lamp out of this material, which we could turn on once, and it would run indefinitely. We could then point this lamp at a solar panel, which would, in the long run, create much more energy than was used turning the lamp on. In fact, it seems it could create an unlimited amount of energy.

This (apparently) violates the laws of thermodynamics, but why is the logic wrong?

user28375028
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The heat that makes a filament lamp glow is derived from electrons bashing into the lattice of atoms in the filament and transferring energy to them. The kinetic energy of the electrons becomes vibrational energy of the lattice, and this is exactly what heat is.

However the interaction of electrons with the lattice is also what resistance is, and superconductors work because they prevent the electrons from interacting with the lattice. Exactly how this happens is a bit involved, but see my answer to Intuitive reasons for superconductivity if you're interested to know more.

So what we're working round to is that a filament lamp made from a superconductor wouldn't light up, because the electrons wouldn't transfer any of their energy to it. That means there's no light to drive your solar panel and no perpetual motion machine. Sorry!

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John Rennie
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  • Excellent answer. We just discussed superconductors in my E&M course for the first time today, and I knew I was missing something. – user28375028 Oct 14 '14 at 16:28