221. How can currents and electromagnets encounter frictional effects without touching?
When you slide a strong magnet quickly above a metal surface, there is a friction-like magnetic drag effect. This effect occurs even when the two objects don't touch. The origin of this effect lies in the repulsions between the metal and magnet: it's strongest slightly in front of the moving magnet so the magnet encounters some difficulty heading forward. The reason why the magnetization of the metal is strongest slightly in front of the moving magnet is related to the loss of energy by current moving in the metal. The magnetization (of the metal surface) in front of the moving magnet is fresher than the magnetization behind it. The current responsible for the magnetization behind the magnet has been flowing for long enough to have lost energy. But the faster you move the magnet across the metal surface, the less time the currents in it have to lose energy and the less friction-like force the magnet experiences.