PHYSICS C10 Lecture Notes - Lecture 22: Cooper Pair, Superconductivity, Geiger Counter
Document Summary
Electrons: a photon or another atom hitting an electron can excite it up from the ground state to a higher lever. Transistor diodes: convert ac current to dc by only letting current go in one direction. Also know as rectifiers: the small black box that is part of the power wire for a computer is a rectifier. Photoelectric effect: quantum phenomenon, known since 1880s, photomultiplier tube. Only works with high-frequency light because only those have enough energy to eject an electron: solar cells use the high-frequency part of sunlight. If you start a current in a superconducting material, the current never stops: innducing a current in a metal by moving it through a magnetic field creates a new magnetic field to oppose the original (lenz" law). Doing this to a superconductor makes such a strong opposing force that the magnetic field is completely expelled from the metal. As a result, the magnetic field will just go around the superconducting material.
