Magnetic Fields & Loops of Current: Explained

[fricke]

**Not a homework question.

In my professor note, it says that:
"If a material causes magnetic field (in parallel direction to the surface charge) below a boundary is not the same as the boundary (in parallel direction to the surface charge) above the boundary, then a surface current is created".

and also:
"all magnetic fields are created by loops of current".

Could someone please explain what do these two statements mean? thank you.

 

[ZapperZ]

**Not a homework question.

In my professor note, it says that:
"If a material causes magnetic field (in parallel direction to the surface charge) below a boundary is not the same as the boundary (in parallel direction to the surface charge) above the boundary, then a surface current is created".

and also:
"all magnetic fields are created by loops of current".

Could someone please explain what do these two statements mean? thank you.

Since you did not elaborate on the level you are at with this class, I can only give you a link on what I HOPE that you are able to comprehend. Look at the derivation leading up to the conclusion at the bottom of Page 4-7 on the tangential component of H.

http://local.eleceng.uct.ac.za/courses/EEE3055F/lecture_notes/2011_old/eee3055f_Ch4_2up.pdf

The answer to your last question is from one of Maxwell equations, i.e. the divergence of a magnetic field is zero (i.e. no magnetic source or sinks). Again, without knowing at what level you are at, I have no idea if you even know the concept of "divergence" or understand the physics behind Maxwell equations.

Zz.

 

[fricke]

thank you very much for the reply and PDF link!