What characterizes a superconductor?

A superconductor is characterized by its ability to exhibit zero electrical resistance when cooled below a critical temperature. This phenomenon allows electric current to flow through the material without any loss of energy due to resistance, which is a significant advantage in various applications, such as in powerful electromagnets or efficient power transmission systems.

When materials are in their superconducting state, they also can exhibit other remarkable properties, such as the expulsion of magnetic fields, known as the Meissner effect. This quality further distinguishes superconductors from ordinary conductors, which invariably lose some energy as heat due to resistance. The occurrence of superconductivity is intricately related to quantum mechanical principles, which contribute to the unique behaviors noticed at low temperatures.

Therefore, the correct understanding of superconductors fundamentally revolves around their remarkable ability to allow current to flow without resistance, contrary to what happens in normal conductive materials.