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Physics, Astronomy & Cosmology / Re: Why does an mri magnet not radiate em?
« on: 24/05/2024 22:35:17 »
The drift velocity of electrons in a conductor or superconductor is minuscule - microns per second. So the acceleration of electrons in a 1 m diameter supercon magnet is negligible and any em radiation would be undetectable.
You could however argue that there is a minimum diameter of superconductor that cannot sustain its current because no electron could complete a loop. But since no energy is dissipated by resistance in a superconductor, the electrons do not require any energy to maintain their drift speed. However the magnetic field inside this sub-critical loop would be very large and probably exceed the critical field above which it cannot remain superconducting.
But I happily admit this is something of a "handwaving" argument and doesn't satisfy my pedantic alter ego.
You could however argue that there is a minimum diameter of superconductor that cannot sustain its current because no electron could complete a loop. But since no energy is dissipated by resistance in a superconductor, the electrons do not require any energy to maintain their drift speed. However the magnetic field inside this sub-critical loop would be very large and probably exceed the critical field above which it cannot remain superconducting.
But I happily admit this is something of a "handwaving" argument and doesn't satisfy my pedantic alter ego.
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