Many folk struggle to understand electricity because it can really be seen so they don't have a real-world way to visualise it. Probably the best analogue for it is plumbing and the behaviour of water (or any other contained fluid like hydraulic oil).
EMF is the driving force for electric current, analogous to the the supply pressure for a water system. Current is effectively the flow of water (Ampere = Coulomb per second, say equivalent to litre/second of water flow) and resistance the effect of pipes to make it harder for water to flow (so proportional the length of pipe and inverse to diameter, approximately, just as conductor size and cable length matter). While not entirely the same, you can also see that too much pressure for the pipe risk it busting the wall and water gong everywhere, same idea as too much volts causing insulation breakdown. Roughly speaking.
So far, so good. What you are asking about is induced EMF from a magnetic field and this is the basis of a generator and transformer. You can look up Maxwell's equations for the detail, but that would be VERY unhelpful here. The key for induced stuff is that the electric field depends on the
rate of change of the magnetic flux that the conductor crosses, same as how the magnetic effect depends on the flow of current (i.e. rate of change of electric charge). There is a magnetomotive force as well, the magnetic version of EMF.
So in something like a generator where you have a wire moving in a magnetic field (physically driven by a steam turbine or whatever the prime mover is) you can quickly see the voltage is going to depend upon the product of:
- How strong the magnetic field is (B)
- Velocity wire is moving relative to B (v)
- Length of wire, typically made in to coils for compact shape (L)
Hopefully you can now answer the question?
