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
Groningen back to 1614. After the University of Leiden, it is the second oldest Dutch university. The university educated the first female student, Aletta Jacobs, the first Dutch national astronaut, Wubbo Ockels, the first president of the European Central Bank, Wim Duisenberg and two Nobel prize winners, Heike Kamerlingh Onnes and Ben Feringa. 200,000 people were either students, teachers or researchers at the university. Groningen has the highest percentage of students by total population, approximately 25 percent. The city council has 39 members. With 9 seats, the social-liberal D66 is the largest party on the council. The social-democratic PvdA has 6