I'm confused how a magnetic pump works as described in my text. I'll quote: """Liquid metals, such as the molten sodium used in certain nuclear reactors, can be moved through pipes using an electromagnetic pump that has no moving parts. If the metal has to be moved in a pipe that is orientated north-south, for example, a large electric current can be sent across the pipe --east to west perhaps. Then, if a strong magnetic field is directed downward through the same section of pipe, the current-carrying metal will be forced to move southward""" This appears to be two magnetic fields, one crossing the pipe also in a horizontal plane to the current, and the other magnetic field directed downward perpendicular to the pipe direction. But I don't understand why you need two. My understanding so far: First Field: If the current is across the pipe east to west, right to left, and the magnetic fields are circular moving north-south along the pipe, the force is already downwards in a vertical sense and not down the pipe. Second Field: A second field vertically downward apparently moves the molten sodium if the force is also southward. I thought that magnetic fields did not interfere with charge, so I'm not following how the molten sodium itself actually moves at all. Why does this need two magnetic fields? Thanks for any understanding.