Flux pinning

Imagine you are playing with a magnet and a piece of paper clips. When you move the magnet close to the paper clip, the paper clip will be attracted to the magnet and stick to it. Similarly, when a superconductor (a special type of material that can conduct electricity with zero resistance) is placed in a magnetic field, it can trap or “pin” magnetic lines of flux.

Now, imagine you have a superconductor in a magnetic field and you try to move it around. The trapped magnetic lines of flux will prevent the superconductor from moving freely, kind of like if you were trying to drag a magnet across a table full of paper clips. This effect of the trapped magnetic lines of flux restricting the movement of the superconductor is called “flux pinning”.

Flux pinning is actually really useful in certain applications. One example is in MRI machines, which use superconducting magnets to create a really strong magnetic field. The trapped magnetic lines of flux in the superconductor keep the magnet from shifting or vibrating, which is important for producing a clear and detailed image.

So, in summary, flux pinning is when a superconductor traps magnetic lines of flux in a magnetic field and is restricted in its movement because of them. It’s also really useful in things like MRI machines.