Electric current certain materials when cooled below a characteristic critical temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of "perfect conductivity" in classical physics. In a semiconductor it is sometimes useful to think of the current as due to the flow
Pieter Rijke 1836. The title of his Ph.D. thesis was "De origine electricitatis voltaicae". In 1835 he was appointed professor of physics at the Royal Athenaeum in Maastricht. In 1845 he became extraordinary professor and in 1854 he was promoted to full professor of physics at the University of Leiden. There he started a physics laboratory with a large collection of scientific instruments. His most important students were H.A. Lorentz and J.D. van der Waals. He retired in 1882, and was succeeded by Heike Kamerlingh Onnes as professor of experimental physics at the University of Leiden. Rijke became a member of the