You could easily now be asking yourself "How could the speed of the bar possibly be constant when there is a force pulling it to the right and the rails are frictionless?" That is a very legitimate question. Since there is a current in the bar, that current will experience a force from the magnetic field. Determine its magnitude and direction. If the bar really is moving at a constant speed, then how large is the applied force? Determine the power supplied by whoever or whatever is pulling the bar. Is your answer consistent with your answer to Question #15? Explain. So a student at your table asks you "Where is the energy delivered to the resistor coming from?" What would you tell that student? In a region with a constant magnetic field as shown, there are two conducting frictionless horizontal rails, a resistor and some conducting wire along the left side and a conducting bar on the right side that is free to slide left or right. The bar is initially at rest but at time zero a force is applied to the bar pulling it to the right so that the distance s increases with time. In Questions # 8-10, we will determine what Lenz Law tells us about this situation. R F L Applied