Question

I need to do this using a different procedure

AS 4 In situation given in problem SP 17, compute the torque that must be maintained on the bar to keep it rotating at a constant speed. One Possible Solution: The current is going radially outward through the bar, so it is perpendicular to the magnetic field. The force on a tiny slice of the bar is directly opposite to its linear motion, which makes it perpendicular to the bar itself. Calling the distance of the tiny slice from the pivot r, we get this drawing: The tiny torque contributed by the force on that tiny slice is: dr =|pxdĒ =rdF sin 90° dt = IB rdr dF = 1dl x B = I dr B sin 90° Now just add up the torque contributions of all the slices (from r = 0 to r = L) to get the full torque, then plug in the current found in part (a): (where I = induced current [Hint regarding alternative solution: The power delivered to a system by a torque is equal to the product of the torque and the rotational speed.]

Answer 1

AS-4 question The solution given in the is totally correct. Alternative solution can't be Applied as we don't have the value as Power delivered to the System and the angular speed so The equal and opposite torque is needed to maintain the motion at the bar at constant speed. so t = 2 B12? clockwise