Superconductors

In a nutshell

Superconductors are a materials that have reached a state called superconductivity where the electrical resistivity drops to zero below a critical temperature. Due to their strong magnetic fields they have many applications.

Superconductivity

As the temperature drops in conductors so does their resistivity due to the positive ions vibrating less and fewer collisions occurring. However, below a specific temperature called the critical temperature $$T_c$$, materials achieve a state of superconductivity. This is a state where the resistivity of the material is reduced to zero.

Below is graph showing the relationship between temperature and resistivity in a conductor:

A Temperature B Resistivity 1. Superconductor 2. Normal metal

The critical temperature is different for every material but is normally many degrees below zero, e.g. mercury has $$T_c=4\ K$$ ($$-269\degree C$$). Scientists are currently working to find a material that has a critical temperature around room temperature since they have many applications.

Applications of superconductors

A very important property of superconductors is that they have very strong magnetic fields. This is because with zero resistivity they can carry a very large current that creates very strong magnetic fields.

They are for example used in MRI scanners which use liquid helium to keep their electromagnets cool, and in maglev (magnetic levitation) trains that use them to keep the trains suspended and greatly reduce friction.