Superconductors are special materials that can conduct electricity with absolutely zero electrical resistance when cooled below a certain critical temperature. This means that electric current can flow through a superconductor indefinitely without any loss of energy.

Under normal conditions, electrical resistance in wires causes energy loss in the form of heat as electrons collide with atoms. However, in a superconducting state, these collisions disappear due to quantum mechanical effects. The electrons form pairs called Cooper pairs, which move through the material without scattering, resulting in perfect conductivity.

Each superconductor has its own critical temperature (Tc)—the temperature below which it becomes superconducting. For example:

• Mercury becomes superconducting below 4.2 K (about –269°C).
• Some high-temperature superconductors, like yttrium barium copper oxide (YBCO), become superconducting above 77 K, the boiling point of liquid nitrogen, making them more practical for applications.

Another fascinating property of superconductors is the Meissner effect, where they expel magnetic fields, allowing them to levitate magnets—an effect used in maglev trains.

Superconductors are used in:

• MRI machines for powerful, stable magnetic fields,
• Quantum computers for low-noise qubits,
• Magnetic levitation transport systems,
• Power grids to reduce transmission losses.