Superconductivity

physics · electricity · extreme cold · materials science

Zero resistance. In a superconductor, electricity flows with absolutely no resistance at all. This means a current can keep moving through a loop of superconducting wire forever and ever, even without a power source.

Needs extreme cold. Superconductors only work when they're cooled below their critical temperature, which is extremely cold (usually near absolute zero). Above that temperature, they behave like normal materials.

Expels magnets. When a superconductor is cold enough to work, it pushes away magnetic fields completely. This is called the Meissner effect, and it's why magnets can actually levitate above superconductors.

Sudden change. Unlike regular metals that gradually lose resistance as they get colder, superconductors flip like a switch. Below the critical temperature, their resistance drops instantly to zero.