Q50: Figure P31.50 represents an electromagnetic brake that uses eddy currents. An electromagnet hangs from a railroad car near one rail. To stop the car, a large current is sent through the coils of the electromagnet. The moving electromagnet induces eddy currents in the rails, whose fields oppose the change in the elec- tromagnet’s field. The magnetic fields of the eddy currents exert force on the current in the electromag- net, thereby slowing the car. The direction of the car’s motion and the direction of the current in the electro- magnet are shown correctly in the picture. Determine which of the eddy currents shown on the rails is cor- rect. Explain your answer.