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
Museum Boerhaave to me in 1921. P. Ehrenfest. ' Museum Boerhaave Museum Boerhaave is a museum of the history of science and medicine, based in Leiden, Netherlands. The museum hosts a collection of historical scientific instruments from all disciplines, but mainly from medicine, physics, and astronomy. The museum is located in a building that was originally a convent in central Leiden. It includes a reconstructed traditional anatomical theatre. It also has many galleries that include the apparatus with which Heike Kamerlingh Onnes first liquefied helium (in Leiden), the electromagnet equipment used by Wander Johannes de Haas (a Leiden physicist) for his low-temperature