Normal Magnetic Field Boundary Conditions
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- เผยแพร่เมื่อ 5 ต.ค. 2024
- / edmundsj
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In this video I use Gauss’ Law for magnetism to figure out what the boundary conditions are across an interface for the magnetic flux density (also known as the B-field), and how this reduces to a simpler form for non-magnetic materials. I also summarize the four boundary conditions we have figured out.
This is part of my graduate series on optoelectronics / photonics, and is based primarily on Coldren's book on Lasers as well as graduate-level coursework I have taken in the EECS department at UC Berkeley.
Hope you found this video helpful, please post in the comments below anything I can do to improve future videos, or suggestions you have for future videos.
This is the best explanation so far. I wish my professor explained like this. Thank you very much!!!!
Very very good. Every university should just run these videos in the lectures.
Thank u so much for giving such wonderful videos to us. ❤
Again, just beautiful...
Thank you
You mentioned at the end that the tangential components are "by themselves", but the tangential component of the H-field has K?
Can you please make a video about imaging methods? There is almost no good video about this topic out there.
Thanks🙏
Sir, Could you please explain more about when K can be regarded as zero?
Ah, yes, wonderful question. K is the surface current density. So if, for some reason, you have a ton of current flowing just on the surface of a material, you can't neglect it. This is quite rare, and I've never actually encountered a case myself where it happens. Topological insulators are one example of where you may have to worry about it, and perhaps when you are dealing with surface plasmons (shining light on metals under certain conditions).
Even if if the height of the cylinder wasn't taken to be zero, because we're considering H_norm, wouldn't the contributions from the sides of the cylinder in the integral still be zero? Because H_norm is perpendicular to the normals from the sides...?
You are correct, the main reason we are taking the cylinder height to be zero is that the magnetic field could change as you go further away from the surface. In general, unless the field is perfectly uniform across all space, this will be the case.
@@JordanEdmundsEECS Thanks a ton.
How's it possible to have B fields going on opposite directions from the interface?
We are just integrating in different directions, the field itself we don’t actually know in which direction it’s pointing on either side (that’s why we’re doing the math). This is just math, not physics.
I have a doubt sir. Why do you consider normal components to be in the same direction?
It doesn't matter. If you assume them in opposite direction then you will get negative sign in final result. which essentially means they are in same direction.
what if they are air/metal interface
hi everyone , can anyone help me about acoustic propagation
It uses essentially all the same math as electromagnetic wave propagation, but instead of the velocity of light (c) you have the velocity of sound. Instead of electromagnetic wave impedance you have acoustic impedance. All the rest of the math is the same, but you also have longitudinal acoustic waves in addition to transverse ones. Reflection at interfaces is the same, and you can use transmission line language basically as-is.
@@JordanEdmundsEECS brilliant equivalence! 😊🙌🏽💯
👍🏼
In short: 7:37