if you prefer to hear more university-like professor presentation about magnetism see the following sets of video
What is Magnetic Flux?
In this video we will explain what is magnetic flux in the magnetic coupling circuit.
Inductor Saturation and its Consequences Explained
prof. Sam Ben-Yaakov explains behaviour of inductor in saturation state and its consequences.
What is Self Induction ?
What is self induction with alternating voltage source in the magnetic coupling circuit ?
Switching Frequency Impact to Ferrite Cores Losses
prof. Sam Ben-Yaakov explains the effect of switching frequency on ferrite cores losses and importance of f*Bpk
lets explain the polarity of the induced voltage.