Real coil
Iron-core inductor in the time-dependent case

The real coil is the seat of non-linear phenomena that complicate calculations enormously. In particular, in the magnetic circuit :

• material saturation: b and h are no longer proportional;

• magnetic hysteresis, which results in a doubling of the b (h) characteristic;

• the appearance of induced currents known as eddy currents.

The last two phenomena give rise to losses in the magnetic circuit, known as hysteresis losses and eddy-current or iron losses.

First, we'll assume that hysteresis and eddy currents are negligible 2.1