Understanding the Meissner Effect

The world of magnetism is downright vast. From astrophysics to arts and crafts, it plays a large role in many areas of life. What we don’t always hear about is the science behind magnetism—the ins and outs of what makes it work and how these theories can be applied.

It’s time for a quick physics lesson. We’ll be taking a closer look at the magnetic phenomenon known as the Meissner Effect. This basic principle (a relative term for all you non-math folks) describes the relationship between magnetic forces at certain levels of heat and strength in the presence of a superconductor.

Superconductivity is defined by having absolutely no electrical resistance, thus superconductors can carry electric currents without energy loss. However, superconductors can only achieve this once hitting a certain temperature. Once they hit this temperature, they expel magnetic fields from their interior. Scientists also noticed that when superconductors are cooled below this temperature, something interesting happens—the magnetic field inside them vanishes. This phenomenon is known as the Meissner Effect.

Named after German physicist Walther Meissner, the effect was first recorded in 1933 by him and fellow researcher, Robert Ochsenfeld. The two men discovered the ability for superconductors to expel magnetic fields from their interior when cooled below their superconducting transition temperature. When superconductors give off no magnetic field, it is referred to as the Meissner State.

When superconductors are in their Meissner state, they are perfectly diamagnetic. In other words, they do not attract magnetic objects. Another way to put it is that these superconductors lose their magnetic flux. Without any magnetic interference, these superconductors can carry current with no resistive loss, though the current is limited by a critical value. That’s why they’re superconductors.  

One way to visualize this is by taking a magnet and holding it near a superconductor in the Meissner State. The magnet will be so repelled by the superconductor that it will appear to float in midair. You can watch a video of it here.

While the Meissner Effect probably doesn’t affect your life on a day-to-day basis, it is an important component in understanding how the world of physics functions. Scientists still don’t fully understand the phenomenology behind superconductors, but as always, magnets help provide some answers!

Read more about interesting magnetic facts and experiments on our blog!