Consider the possibility of a new design for an electric train. The engine is driven by the force on a conducting axle due to the vertical component of the Earth's magnetic field. To produce the force, current is maintained down one rail, through a conducting wheel, through the axle, through another conducting wheel, and then back to the source via the other rail. What current is needed to provide a modest 10 kN force? Take the vertical component of Earth's field to be 10 µT and the length of the axle to be 3.0 m. At what rate would electric energy be lost for each ohm of resistance in the rails? Is such a train totally or just marginally unrealistic?

Consider the possibility of a new design for an electric train. The engine is driven by the force on a conducting axle due to the vertical component of the Earth's magnetic field. To produce the force, current is maintained down one rail, through a conducting wheel, through the axle, through another conducting wheel, and then back to the source via the other rail. What current is needed to provide a modest 10 kN force? Take the vertical component of Earth's field to be 10 µT and the length of the axle to be 3.0 m. At what rate would electric energy be lost for each ohm of resistance in the rails? Is such a train totally or just marginally unrealistic?