# how much energy does it take to reverse the poles of a manet?

I'm looking into the idea of creating an electro-permanent magnet using two magnets. One alnico and one neodynium. The principle is if you reverse the poles of one magnet you can essentially switch the magnet on and off (like this video).

Presumably alnico is used because of its lower coercivity. So that it costs less energy to do this.

The question I have is how much energy does it take to permanently flip the alnico magnet or indeed any ferromagnetic material in general? How much energy do we save by using the electro-permanent trick above?

Ideally I'm looking for a formula given an answer in Joules given dimensions of the ferromagnet, number of coils and coercivity?

How do you relate the remanence to the to the energy applied? (how much energy is wasted / what is the efficiency?)

Does flipping the polarisation take significantly less energy than first demagnetising (reducing the remanence in one direction) and re-magnetising (increasing the remanence in the other)? If so why?