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Sick of ridiculous KVL infighting

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RoGeorge:

--- Quote from: Nominal Animal on January 17, 2022, 06:05:43 am ---e.g. \$\pi = 3.14\$

--- End quote ---

Can be between 3 and 4, according to mathematicians:  ;D

When Pi is Not 3.14 | Infinite Series | PBS Digital Studios


though Pi is 3.0 for construction engineers and that's nothing but a scratch, because cosmologists often assume Pi is 1.0!  :scared:

PlainName:
Her hands need tying down or the video cropping or something. Very hard to watch with those beating time.

RoGeorge:
She was a very good host for that channel, that good that after she left the channel in order to have more time to finish her PhD, they tried a few replacements but none were as charismatic and skilled as she was, and after a few more months of trying, PBS decided do end the "PBS Infinite" channel.

"PBS Infinite Series" was a very good channel, always with outstanding content and making complicated concepts easy to follow, brief but showing just enough to make one curious and wanting to learn more.

RoGeorge:

--- Quote from: Nominal Animal on January 17, 2022, 06:05:43 am ---you do get from QED to Maxwell's equations at the limit of taking the reduced Planck constant to zero, \$\hbar \to 0\$.

--- End quote ---

He, he, nice!  I didn't know that before, so I've thought "how's so" while peeling potatoes, trying to cherry-pick for an explanation.  Well, \$\hbar \to 0\$ would mean making quantization smaller and smaller, until instead of quantities coming in certain chunks, it all become a "smooth" continuous function, just like we used to have before QED.  Q.E.D.  ;D

But the idea of energy coming in chunks was introduced in order to patch the wrong prediction of the so called ultraviolet catastrophe.  With smooth energy exchange, the calculated spectrum of a black body radiation was very different from the measured spectrum.  And somehow, adding a new rule about energy exchanges happening only in certain chunks of energy, the quantization, fixed that wrong prediction.

Now, I would expect to get some failed prediction in terms of QED, too, when \$\hbar \to 0\$ (as it is in Maxwell), similar with the failed predictions from the spectrum of the black body radiation when the quantization aspect was not considered, but I don't know any examples where Maxwell fails to predict correctly.

What would be such an example?

bsfeechannel:

--- Quote from: Simon on January 16, 2022, 09:51:35 am ---You don't need a degree in physics to know that you should not route a trace from one ground plane to another, this is because you don't need to know down to the atomic level why it's a bad idea, at a basic level you just need to know not to do it, a slightly better engineer will know the verbal reasoning but won't need to worry about the math. It is the physicists job to tell you the math detail but for the purposes of designing a PCB that's irrelevant, because as a good engineer you know not to do it.

i have no idea about fields, but I put items including a SMPS through military EMC testing successfully, no physics knowledge required, I'm just a good engineer. If you asked to to prove down to the math why my method worked I will tell you to consult a physicist. I can tell you broadly what is going on but I won't be calculating the rf emissions for you. No one sits down and makes calculations to that level when they design for EMC, they learn what works and what does not and hopefully get mentored by anther experienced engineer. Theoretical evaluation of an EMC scenario is far more complicated than designing with well informed instinct based on intuition and experience. That is the difference between engineers and physicists.

So as he is the ultimate physicist why did he do a demo to disprove a theory but not explain that the theory was not meant to hold at this level and then explain what was going on. He just seemed to disprove someone with no explanation himself.

--- End quote ---

"All generalizations are dangerous. Even this one." People attribute to Alexandre Dumas. We can't generalize and say that knowledge of physics is dispensable for the "good" engineer. Electronics engineering is a vast field. Some areas can get away with basic knowledge of circuits. Other areas are at the edge of the technological advancement and require really knowledgeable people.

So, the difference between an engineer and a physicist not always can be translated into the knowledge of physics. And in many cases you can have a bit of overlap between the two camps. Just to cite two classical examples, Michael Faraday, a physicist, while discovering the phenomenon of magnetic induction invented the very first transformer, which is now an ubiquitous engineering device. Moritz Jacobi, an engineer (and also a physicist) proved the theorem of maximum power transfer.

Lewin never wanted to disprove Kirchhoff's laws. What he wanted to show is that those laws are not applicable to all circuits and in that case the more general theory is Maxwell's equations. He left the explanation of his demo as a homework to his students. The "ridiculous" KVL threads we have is us responding to the challenge, and discussing why some have flunked it miserably. I have learned an awful lot with it, especially with Sredni's and Huronking' posts and with several others'.

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