Final answer:
The change in flux in a circuit can lead to the average induced voltage. Multiple-loop coils and an iron ring can enhance the observation of induced emf in Faraday's apparatus. The equation emf = -N(dΦ/dt) expresses the relationship between induced emf, the number of turns in the coil, and the rate of change of magnetic flux.
Step-by-step explanation:
The change in flux in a circuit can lead to the average induced voltage. When there is a change in current in one coil, it induces an electromotive force (emf) in another coil.
This can be expressed using the equation emf = -N(dΦ/dt), where N is the number of turns in the coil and dΦ/dt is the rate of change of magnetic flux.
For example, in Faraday's apparatus with multiple-loop coils and an iron ring, the change in flux is enhanced. The multiple-loop coils allow for more turns, increasing the emf.
The presence of the iron ring helps to concentrate and contain the magnetic field, further enhancing the induction process.