This question comes from the equation E = vB (moving conductor in a magnetic field -- E = electric intensity, v= speed of the conductor's movement, and B = magnetic field strength). Say B is constant, so the only thing we have to rely on to vary the electric intensity in the conductor is its speed. The faster you move the conductor, the more potential difference you set up in the conductor -- the magnetic force pushes the charge in the conductor to move to one of its ends and thereby set up the voltage. Now, the question, roughly, is: What if only a finite charge can be moved within a conductor and therefore only a finite voltage can be set up? (if the voltage is finite, then E is finite -- and if E is finite, it means there's a value of v beyond which the above equation won't work) This question came to my mind from the -- misconception (probably) -- fact that in a step-up transformer, a high p.d is set up with only negligible current flowing because all the charge is used up to set up p.d. I have a feeling my understanding is wrong on some really fundamental level. Key concepts which I have a feeling I have wrong are of voltage and electric intensity. I'll be grateful if you can help clear my concepts.