a rectangular wire loop located in the plane of the page has a width l, and its length, x, is determined by the position a movable rail that forms the fourth side of the rectangle, as shown. the total electrical resistance of the wire loop is r, and an externally applied magnetic field, b, is directed out of the page. the rail is moving towards the right with speed v. assume that the x direction is towards the right of the page, the y direction is towards the top of the page, and the z direction is out of the page.