Critical Field in a Superconducting Solenoid

Question

Suppose you have a superconducting wire with a constant current below the critical current and a resulting magnetic field below the critical magnetic field. If you were to wind the superconducting wire into a solenoid, the magnetic field would increase even though you haven’t added current. If you were to add enough windings so that the uniform magnetic field inside the solenoid were to exceed the value of the critical magnetic field, would the wire love superconductive properties?

HolgerFiedler · Answer

The magnetic field of a superconducting wire is generated by the electrons in the wire. When winding into a coil, the effect is self-reinforcing, the magnetic field of the coil increases.
The magnetic field of the coil does not destroy itself by winding the coil. On the contrary, the magnetic field stabilizes itself.
What can destroy the magnetic field of a superconducting coil is an increase in temperature or an external magnetic field:

The increase in temperature is equivalent to a higher mobility of the subatomic particles and a disorientation of their magnetic moments. The magnetic field is lost.
An external magnetic field also influences the magnetic orientation of the subatomic particles and, above a critical strength, can irreversibly change the order of the particles. The magnetic field of the coil is destroyed.

Critical Field in a Superconducting Solenoid

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