What is hysteresis loop?

Our teacher gave this in a worksheet, but never explained it in class.
Our teacher gave this in a worksheet, but never explained it in class.
Hysteresis loop is basically a graph in magnetism. To understand how it forms and to make things clear, first we need basic understanding of some magnetic terms
Now, consider a completely demagnetised ferro magnetic material (for which, B=H=0). If we subject this material to increasing values of H and measure the corresponding values of B, it will form a graph as shown below. [4]
After a point ( b in this case), if we try to increase the value of H, B won't get increased anymore. This point is called saturation point. If we decrease the value H, the curve follows b-c path. Which means, the material will have some value of B even the value of H is zero. This is called remanent flux density.
If we further decrease H, it will decrease upto point d. Here B becomes 0.
If we further decrease H down, the curve follows the path d-e, increasing H in reverse direction and stops at the saturation point, e.
If H varied backwards, then the curve follows e-f-g-b path as shown above.
The loop formed is called as hysteresis loop. Using this loop, we can determine various properties of a material such as retentivity, permeability, and reluctance [5]
[1] https://whatis.techtarget.com/definition/magnetic-field-strength
[2] https://simple.wikipedia.org/wiki/Magnetic_flux
[3] https://en.wikipedia.org/wiki/Ferromagnetism#Ferromagnetic_materials
[4] http://www.electricalbasicprojects.com/what-is-hysteresis-loss-hysteresis-loop/
[5]
https://www.nde-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/HysteresisLoop.php