1. The problem statement, all variables and given/known data Hi all. I can't seem to understand how to apply Lenz' law to a disc rotating in a magnetic field that is perpendicular to the discs plane (see first page on PDF): http://www.pa.uky.edu/~latimer/phy232s08/lectures/phy232l31_4.pdf [Broken] I can see that using the right-hand rule, positive charge will build up on the edge and negative at the center. So an EMF will run from the outer edge to the center, but I can't seem to relate this to Lenz' law. The change in magnetic flux will just get larger because of the induced EMF, and not opposed?