# What happens to the temperature of a superconductor?

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## Summary:

In the following setup, what would happen to the temperature of the superconductor after on cycle?
Consider the following setup:

Stationary magnet and Superconductor are fixed and Moving magnet is allowed to move freely in the horizontal direction.
Assume the superconductor as Type I superconductor.

Following figure shows the Horizontal Force acting on Moving Magnet vs Distance curve:

Red is when Superconductor is at temperature greater than critical temperature of superconductor (T > Tc).
Blue is when Superconductor is cooled down to a temperature less than critical temperature of superconductor (T < Tc).

Switching of superconducting state using Temperature in Meissner motor is discussed by A Takeoka et.al (1989).
Switching of superconducting state using Current Density in Superconductor actuator is discussed by Y Kim et.al (1989).

However, any device using switching of superconducting state using magnetic field is not discussed in the literature to my knowledge.

If we switch superconducting state of the superconductor from on to off, is it possible to switch from blue curve to red curve after the half cycle?

Following is an illustration of magnetic field distribution with shaded region having H > Hc:

What would happen to the temperature of superconductor after one complete cycle?
Early papers from Keesom shows the drop in temperature. Any confirmation or discussion would help.
Need understanding of complete thermodynamic cycle of the superconductor.

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mfb
Mentor
Following figure shows the Horizontal Force acting on Moving Magnet vs Distance curve:
That doesn't look right, in particular it should be asymmetric based on the sketch.

That doesn't look right, in particular it should be asymmetric based on the sketch.
The figure is just for illustration. Yes, it should be asymmetric when the superconductor is in superconducting state and symmetric when it is not. Also the ends would flatten.

One can obtain these results from any commercial software, I used flux software.

The point is that the net area in both cases is zero. But the total area is greater with blue curve than red curve. Agree?

mfb
Mentor
The point is that the net area in both cases is zero. But the total area is greater with blue curve than red curve.
Looks plausible. The point where the force switches its sign will differ between the two scenarios.

Looks plausible. The point where the force switches its sign will differ between the two scenarios.
Absolutely, the switching point differs.