Superconductivity is a physical phenomenon observed in certain materials where electrical resistance drops to zero when the material is cooled below a characteristic critical temperature. In a normal conductor, such as copper, electricity encounters resistance which is converted into heat, leading to energy loss. A superconductor, however, can carry an electric current indefinitely without any energy loss. Another hallmark of superconductivity is the Meissner effect, which is the expulsion of a magnetic field from the material as it transitions into the superconducting state. This causes the material to repel magnets, a property used in technologies such as maglev trains. Despite these remarkable properties, the practical application of superconductivity is limited because most known superconductors require extremely low temperatures, often near absolute zero, to function, requiring expensive cooling systems like liquid helium.