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
What Katy Did School (set in Hanover, New Hampshire); "What Katy Did Next", in which a new friend of Katy's takes her on a once-in-a-lifetime trip to Europe; "Clover", in which Katy is married and Clover accompanies her brother Phil to Colorado after he falls ill; and "In the High Valley", which shows the lives of a handful of young people living in the High Valley in Colorado, including Clover, Elsie and their husbands. What Katy Did What Katy Did is an 1872 children's book written by Sarah Chauncey Woolsey under her pen name Susan Coolidge. It follows the adventures of a twelve-year-old