Faraday's law
Also called Law of induction
The law of induction: the emf induced around a loop equals the rate at which the magnetic flux through that loop changes. A steady magnetic field, however strong, induces nothing at all.
The AP Physics 2 sheet prints it in absolute-value form only:
The CED adds the signed version at 12.4.A.4, , where the minus sign is Lenz's law. AP Physics C: Electricity and Magnetism writes the same statement as a derivative and as Maxwell's third equation, , and prints a separate solenoid form carrying the turn count .
Rate of change is the whole content. Not the size of the field, not the size of the flux. Park a loop in the strongest steady field available and the induced emf is zero. Halve the time over which the same flux change happens and you double the emf.
Since , there are exactly three levers: change the field strength, change the enclosed area, or rotate the loop. A generator is the third one done continuously.
Two things to keep straight. No turn count appears anywhere on the AP Physics 2 sheet, so an -turn coil is not a Physics 2 quantitative case. And an emf is not a current: a loop that is not a closed conducting circuit still has an emf induced around it, with no current to show for it.
Topic 12.4 owns the procedure, including the rod-on-rails case and its derived .