+1 on Steve's pronouncement. Imagine you're a stationary electron sitting in a stationary wire making up a coil (of course, in reality, electrons are like my grandsons -- they can't sit still). The force you feel is proportional to any electric field present. The electric field E the electron sees is related to the time rate of change of the magnetic field. Your goal, Mr. Phelps, is to maximize the magnitude of the magnetic field at right angles to the direction of motion of the magnets so that the B field changes as rapidly as possible with movement. However, the secretary will disavow any knowledge of your actions.
You can also look at the force on the electron sitting in a loop of the wire as the wire moves through the (static) field created by the permanent magnets (and use the Lorentz force with the velocity of the electron crossed into the static B field of the magnet). To make this force as large as possible (which creates the most voltage), you want B's magnitude as large as possible. In both cases, the two magnets have to be attracting each other to get the biggest B field in between them.
See
here for more info if you're interested.
As a student, I remember playing with the school's electromagnet. I machined some pole pieces for it from some 4 inch diameter steel bar stock (that's an interesting story where I nearly killed myself) and then installed them. Then we'd turn up the current in the coils and drop pieces of brass and aluminum between the poles (czechs on the weekends). The eddy-current slow-down never failed to entertain students, teachers, and secretaries.
