Demonstrate magnetic repulsion and the "right hand rule" of magnetism with this unique kit. Two rails are electrified, generating a magnetic field and causing a small roller to shoot across the rails and even uphill. The device consists of a plastic base with battery holder and magnet installed beneath, tow rails, switch to change the direction of the electrical current and rod (roller). The magnet beneath the rails reacts with th emagnetic field generated around the roller and produce enought force to propel the roller along the rails, even uphill. You need 4 alkaline AA batteries not included.