Week 9 Paramagnetism & Ferro Magnetism

Question 1

what are two key difference between paramagentism and diamagnetism

Answer 1

paramagnetism and diamagnetism go in opposite directions to each other
para increases field inside the magnet whereas dia decreases it

Question 2

what is the bound current density equation and the surface current density equation

Answer 2

j bound = ∇ x M

j surface = M x n^

Question 3

what is the free current density equation

Answer 3

j free = ∇ x (B/μ0 - M) = ∇ x H

Question 4

what is the magnetic intensity equation

Answer 4

B = μ0(H + M)

Question 5

what is the magnetic energy intensity equation

Answer 5

U = 1/2 ∫B*H dV

Question 6

what is the magnetic field intensity equation

Answer 6

B = μ0μrH

Question 7

what are the two magnetic boundary conditions

Answer 7

H parallel is continuous across a boundary

B perpendicular is continuous across a boundary

Question 8

why do magnetic dipoles align

Answer 8

to reduce energy

Question 9

what destroys the magnetic alignment and what does it imply

Answer 9

thermal fluctuations destroy the alignment

suggests there is a critical temperature

Question 10

how does temperature affect magnetism

Answer 10

as temperature decreases below the curie temperature magnetic domains become more well defined until they merge becoming a ferro magnet

Question 11

what are the three key characteristics of an ideal ferromagnet

Answer 11

M is constant
j surface is non zero
H field lines point towards or away from boundary