When energizing a solenoid, why does an iron object travel along the axis of the solenoid?... and why does it typically get sucked inward no matter the polarity of the solenoid windings? This is a similar question: Why do relays work with both polarities? How does energizing the coil cause the switch's pole to come in contact with the throw, no matter what the polarity? I do, however, understand the jumping ring. When the ring is placed around the outside of a solenoid, and the solenoid is energized, the ring will develop a current to oppose the suddenly-changing magnetic field caused by the solenoid. According to Ampere's law, parallel conductors with oppositely-traveling current will repel each other. The cross product formulas make sense for THAT.... still not understanding the first two though. Thanks for the help.