A great way to introduce students the the right-hand rule and 3-dimensional physics. The Lenz rail consists of two parallel metal rails that are connected to a dc power supply such as a battery (6-18V DC) or laboratory power supply (not included). The parallel rails can be re-positioned to vary the length between the rails. The unit is supplied with 2 conductive metal cylinders, 2 magnets, sandpaper and connecting wires.
The magnets above and below the parallel rails create a vertical field. The current moves perpendicular to this magnetic field and the net force on the charges (therefore the rolling conductive metal cylinder) is perpendicular to both of these (current and magnetic field) and moves away.