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Magnetic effects

The magnetic effects are caused mainly by the spin of the electrons of which the matter is

composed, sometimes by the orbital motion of the electrons in the atoms, and sometimes

by the spin or motion of the other particles. The fields are however always describable by

giving a magnetic medium a density per unit volume of magnetic dipole moment which

we cali M and which gives rise to magnetic fields in the same way as P gives rise to electric fields. Thus the first and fourth Maxwell's equations are modified to V H = 0-V-M (4.18)

VxE = -

ó(poH)

ót-

ó(|ioM)

ót

.(4.19)

Introducing the vector

magnetic Flux Density B = po(H+M) (4.20)

the above equations can be written in the morę compact form

VB = 0(4.21)

VxE = -

dB

ót