General > General Technical Chat
"Veritasium" (YT) - "The Big Misconception About Electricity" ?
bsfeechannel:
--- Quote from: TimFox on March 23, 2022, 03:38:39 pm ---In RF, you will see Z = R + jX all the time in impedance calculations.
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That's what the Smith Chart is all about.
Found in whatever cheap ass VNA, whose mention you find scattered all over this forum, for instance.
Or in professional multi hundred thousand dollar equipment.
adx:
Paradoxical blinking stare.
I will have to have a think about it. But I stand by everything I said because I "feel" I am right - for now. Your post(s) is a perfect illustration of my point.
To Timfox, I didn't say RF engineers don't use j (actually I did a couple of posts back, but in different context), just that I suspect they don't believe it, having risen above it, to the point they realise sqrt(-1) has no physical relevance, with j being the unit vector that I say it is.
bsfeechannel: Seen your post come in. Yes j appears in a couple of places, as an annotation. I was thinking of cheap ass VNAs and Smith charts when I made my claim.
HuronKing:
--- Quote from: adx on March 23, 2022, 11:05:16 pm ---Paradoxical blinking stare.
I will have to have a think about it. But I stand by everything I said because I "feel" I am right - for now. Your post(s) is a perfect illustration of my point.
--- End quote ---
Well you're not in my classroom. I'd do a much better job of explaining it there than in a forum post whipped up over lunch break at work. ;)
--- Quote ---To Timfox, I didn't say RF engineers don't use j (actually I did a couple of posts back, but in different context), just that I suspect they don't believe it, having risen above it, to the point they realise sqrt(-1) has no physical relevance, with j being the unit vector that I say it is.
--- End quote ---
I know you're talking to TimFox but I'm telling you that you don't need to suspect anything. I got training from RF engineers - they do believe it (you have to enter it into the simulation software!) and it has immense physical significance, just as 'zero' and 'negative' have immense physical significance. :D
PlainName:
--- Quote ---Or in professional multi hundred thousand dollar equipment.
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Blimey, and they couldn't even number the ports sequentially. The mere thousands of dollars ones probably leave the labels off.
penfold:
--- Quote from: HuronKing on March 23, 2022, 09:19:22 pm ---[...]
Now this I absolutely agree with. The difficulties are in the pedagogy. sqrt(-1) is called an 'imaginary' number or a 'complex' variable but these names are strictly historical. We can blame Rene Descartes for coining the term 'imaginary' as a derogatory term to imply they are not useful numbers. Those names have no bearing on what the sqrt(-1) actually represents - and it IS a physical phenomena. It's no less 'real' than negative numbers are 'real...' or how some ancient mathematicians regarded zero as a meaningless number...
Like, what if I asked you to calculate the power supplied by a voltage source? But then you did everything right and discovered the value of the wattage is negative! Is that not a 'real' answer? Of course it is. All it means is that I tricked you in the problem statement - the voltage source is absorbing power instead of delivering power.
[...]
--- End quote ---
Nice try... maths just isn't that simple. It is kinda unrelated to negative and zero numbers: the algebra and arithmetic of real numbers and vectors as we know them today are defined, metric spaces, isomorphisms, and all that are properly axiomatically defined; the ancient interpretations were more from ill-formed and contentious philosophical bases which would lead to a disagreement. In contrast to that, the 'imaginary' unit, more generally, abstractly-describes translations between the mathematical representations of two 'real' quantities, e.g. phase angle... the imaginary unit is in itself not a physical quantity.
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