In one of my homework questions, I was given the following setup. I was asked to determine if the induced current flows from X to Y, or from Y to X.
From Lenz's Law I know that the current in the tube flows in the direction opposite to R to oppose the change in flux due to the rotation of the tube in the direction R. However, I am completely lost as to how to determine the direction of current flow across XY. It seems that the charges on the tube along XY are always parallel to the flux field of the magnet. Because of this, no emf should be induced across XY by Faraday's Law.