Faraday’s law, Electromagnetic induction, Electromotive force

The meaning of Faraday's electromagnetic induction experiment is often explained by a model as shown in Fig. (a). The phenomenon of electromagnetic induction is described by the following dynamic equation including the time derivative with respect to Ampere's static integral law.

Here, "e" on the left side is a voltage generated by temporally changing the flux linkage ψ, and is referred to as the electromotive force. The flux linkage ψ is the physical quantity obtained by multiplying the magnetic flux φ by the number of turns, N. As explained in (b), φis the two-dimensional (surface) integral of B・n across the magnetic flux as given by

If we combine the above two relationships and express it in differentiation form with respect to spatial locality, we get the following:

And this is how it is described in many textbooks.

(a) What is electromagnetic induction? Even if there is no electrical connection between the primary winding and the secondary winding, if there is a magnetic interlocking relationship, a voltage is generated between the secondary winding terminals due to the current on the primary side, and it flows.