A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts rolling railgun demonstration (youtube) that permit a large electric current to pass through the projectile. This current interacts with the strong magnetic fields generated by the rails and this accelerates the projectile. The U.S. Navy has tested a railgun that accelerates a 3.2 kg projectil… (More on Railgun)