refer figure A conducting cross bar of mass m and length L can slide without friction up or down on two conducting rails. The rails are connected on the bottom via a variable resistance R and battery E, so that the rails and the bar form a rectangular conducting loop. A uniform magnetic field B points into the plane of the loop. Initially the bar is at rest. What is the total force acting on the bar, moving up at speed v? I am not able to get the book answer, so please solve it.

refer figure

A conducting cross bar of mass m and length L can slide without friction up or down on two conducting rails. The rails are connected on the bottom via a variable resistance R and battery E, so that the rails and the bar form a rectangular conducting loop. A uniform magnetic field B points into the plane of the loop. Initially the bar is at rest. What is the total force acting on the bar, moving up at speed v?


I am not able to get the book answer, so please solve it.