Hysteresis and B-H relationship

Question 1

What is hystereris

Answer 1

loss in the machine

Question 2

magnetic domain definition

Answer 2

atoms of metal (cobalt, iron…) that have their magnetic fields closely aligned

Question 3

what happens when no external magnetic field is applied

Answer 3

each domain has own magnetic field making a small permanent magnet but orientation is different to a neighboring domain so faraday effect cancelled

Question 4

what happens when external mag field applied (DC input)

Answer 4

all domains start to re orient themselves with common field, raising flux density,

as H increases initially, B increases proportionally in B = mu*H

as all domains become oriented same dire, B stops increasing and saturation occurs

Question 5

reverse external mag field (ac input)

Answer 5

H reverses and becomes -ve, some domains move orientation most domains are still in +ve direc (takes time) so some positive flux exists

at point where H becomes large enough -ve dir to reverse all domains, and flux becomes negative and increases in the -ve direction

as H becomes positive again it moves in the oppositive direction so B becomes positive

Question 6

how does applying and reversing external mag field (Ac) cause loss of energy

Answer 6

Hysteresis loop from changing B which causes loss, Ideal form is a linear line instead of loop, energy is lost every cycles due to internal friction