Hand crank generators are the simplest of generators, they're much like other generator but instead of the initial power coming from another source it's coming from you. Hand crank generators are based on the principles of magnetism founded by Michael Faraday. As seen in the image below if you move a conductive wire through a magnets magnetic field (in this case spinning on a drill) you create power. This is a very simply yet effective method, hand crank generators can also be any size you can have a small portable one or a giant one. The voltage increases as the number of turns of wire on the coil, the size of the coil and the strength of the magnetic field increases.