suprajohtavaa

Suprajohtava refers to the phenomenon of superconductivity, a state of matter where a material exhibits zero electrical resistance and expels magnetic fields. This remarkable property is observed in certain materials when they are cooled below a specific critical temperature. The absence of electrical resistance means that an electric current can flow through a superconductor indefinitely without any energy loss.

The discovery of superconductivity dates back to 1911 when Dutch physicist Heike Kamerlingh Onnes observed it in mercury at a temperature of 4.2 Kelvin (-269 degrees Celsius). This phenomenon is explained by the BCS theory, which describes superconductivity in terms of Cooper pairs – pairs of electrons that are bound together by lattice vibrations. These Cooper pairs can move through the material without scattering, thus leading to zero resistance.

Superconductors have a wide range of potential applications. These include powerful electromagnets used in MRI machines and particle accelerators, high-speed trains levitated by magnetic fields, and highly efficient power transmission lines. However, the need for extremely low operating temperatures has limited their widespread use. Research is ongoing to develop high-temperature superconductors that can operate at more accessible temperatures, which would revolutionize many technological fields. The expulsion of magnetic fields, known as the Meissner effect, is another defining characteristic of superconductors and is crucial for their levitation capabilities.