What cause potential difference in the conductor? I mean why the changing magnetic flux induce EMF? I understand the basics but I can't understand it. What I know: there is free electrons on the surface of a copper conductor. Electron have electric field vector and magnetic field vector and these are perpendicular. Electric vector point to the protons/core usually but these are delocalized electrons. In a changing magnetic flux these electrons always turn to the opposite side of flux with their magnetic vector but don't move. That's all, just turn. Why build it EMF? Where is the potential difference?