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One of the amazing 'killer apps' of a cheap, non-toxic, high-temperature superconductor is storing electrical energy in a large current that loops around indefinitely.

If this could be scaled down, it could result in a 'superconductor battery' for your laptop, or whatever.

But, does actually USING the electricity in your smartphone or whatever 'use up' the electricity?

Or would it never need to be recharged?

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    \$\begingroup\$ A flywheel that has no friction still slows down whenever you extract energy from it. It only spins forever if you leave the energy in it, in it. Zero losses doesn't mean energy producing. \$\endgroup\$ – DKNguyen Feb 16 at 16:21
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    \$\begingroup\$ "Conservation of Energy".... one of the fundamental physical laws. You can't extract energy from a system w/o that system losing energy. \$\endgroup\$ – Kyle B Feb 16 at 17:00
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    \$\begingroup\$ Hmm, wouldn't high-current superconductor loops also produce a strong magnetic fields? That's how MRI scanners tend to create theirs. I wonder if that's very practical for a laptop battery... \$\endgroup\$ – marcelm Feb 16 at 17:15
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    \$\begingroup\$ @marcelm Anything with too strong a strong external magnetic field is not permitted on most aircraft. We had to make modifications because the field caused by some fancy gadgetry which shall go unnamed was capable of disturbing the (backup) magnetic compass by more than 2°. \$\endgroup\$ – Spehro Pefhany Feb 16 at 17:45
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    \$\begingroup\$ I’m voting to close this question because it's another of those free energy questions without any research. \$\endgroup\$ – Andy aka Feb 16 at 17:49
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Energy stored in a magnetic field is extracted when you use it, and the field weakens. This is a bit of a simplification but close enough.

The energy in an inductance L is E = \$0.5I^2L\$. To store much energy that way relative to a battery you would need a lot of inductance and/or a lot of current. All superconductors have limits in current density and limits in magnetic field (and lower limits in combination) so you can only go so far depending on the material, temperature (colder is better) and whatever enormous pressures you can subject it to (more pressure is better).

It's not clear to me how you would extract the energy- usually energy in a superconducting magnet comes out as heat when the material goes normal (quench) and boils off a lot of cryogens quickly. That's not the most desirable form of energy. Getting it out as electricity without losing too much of it (as in the typical heat switch used in superconducting circuitry) might be tricky.

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Yes, of course. When you redirect some of the electrons so they go through your laptop, the laptop pushes back against them, which decreases the speed of their looping (i.e. decreases the current). Eventually the current stops completely, and then you have no more energy. Your superconductor battery is now flat.

To recharge it, you have to push the electrons to make them start looping again. That is what a charger does. And the longer you push them for, the faster they go.

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