Changing electromagnetic fields

Static electric fields are independent of static magnetic fields. In dynamic electromagnetic fields changing electric field induces changing electric field and vice versa.

Faraday’s law

Faraday’s law of electromagnetic induction states that the electromotive force (voltage) induced in a loop is equal to the change of magnetic flux through the loop in time. The flux can be changed by physically moving the loop or changing the current through the loop. The minus in the equation below has to do with the polarity of induced voltage (and the direction of induced current) that we will discuss in the next section on Lenz’s law.

The electromotive force can be found by taking a line integral of the induced electric field (by the flux) around the closed loop.

Equating the above two equations, we get Faraday’s law of induction.