EEVblog > The AmpHour Radio Show
#562 – Electroboom!
jesuscf:
--- Quote from: emece67 on January 13, 2022, 06:18:44 pm ---In case anybody is wondering about drilling ferrite cores, keep in mind that they are really hard to drill (that's is, it took me ~1 h to drill 6.5 mm |O )
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Also very brittle!
Sredni:
--- Quote from: jesuscf on January 13, 2022, 06:41:12 pm ---
--- Quote from: Sredni on January 13, 2022, 12:16:37 pm ---
--- Quote from: jesuscf on January 12, 2022, 03:11:54 pm ---Also, do you remember that time you asked me if I had a toroid? Well, I have one now!
--- End quote ---
The induced field generated by a toroidal core is not circularly symmetric around the section of the core. It's more like the magnetic field generated by a single loop of current:
The induced field is stronger inside, being maximum on the axis of the toroid, where all 'cross sections' of the core contribute constructively and decreases faster than 1/r at the exterior. Therefore, your circular ring - even if it is perfectly circular and perfectly concentring to a perfectly circular cross-section core - will not experience the same Eind field in all points of its circumference.
The infinite long solenoid, with its perfectly circular Eind field lines, on the other hand, allows you to pull the trick of considering the contribute on arcs of equal length to be the same. But a toroidal core? No.
Therefore your answer about having
--- Quote ---VA_to_R1=16.9mV
VR1_to_D=16.9mV
VD_to_R2=16.9mV
VR2_to_A=16.9mV
--- End quote ---
in the approximately circular ring around your square section core is... you guessed from the preview... WRONG.
And this is where I wanted to take you - and Jesse - some ten-fifteen pages ago when I asked you to specifiy your 'McDonald voltages' for all parts of that 'killer question' circuit that Jesse kept reposting. But you guys ran away like politicians from a truth serum.
Like you seemingly did when I asked you to explain why Hayt - which defines voltage as the path integral of the electric field - makes a difference between potential difference (to be used in the static case) and voltage/emf (to be used in the dynamic case).
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You seem to agree that in my setup VA_to_R1=VR2_to_A and VR1_to_D=VD_to_R2. Is that correct?
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In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
In your world, if by V you intend the scalar potential difference... Good luck! Unless you have perfectly symmetric rings perfectly centered around a perfectly symmetric core, you need to resort to numerical computation to get their values.
Moreover, when variable magnetic fields are present, the scalar potential difference does not give the full story. It is a partial result in that it describe only a part of the actual electric field in the ring.
Have you started reading Hayt, yet?
ogden:
--- Quote from: Sredni on January 13, 2022, 10:41:12 pm ---In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
--- End quote ---
Engineer just measured 12VAC on transformer output. Wannabe scientist: as resistance of transformer secondary winding is zero, then voltage on terminals of transformer secondary is I*R meaning - zero. [edit] Those guys claim to know Faraday's law? C'mon.
Sredni:
--- Quote from: ogden on January 13, 2022, 11:08:20 pm ---
--- Quote from: Sredni on January 13, 2022, 10:41:12 pm ---In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
--- End quote ---
Engineer just measured 12VAC on transformer output. Wannabe scientist: as resistance of transformer secondary winding is zero, then voltage on terminals of transformer secondary is I*R meaning - zero. [edit] Those guys claim to know Faraday's law? C'mon.
--- End quote ---
We really are back to square one, aren't we?
In my world voltage is path dependent so I can have zero voltage ALONG the coil filament, and 12 V ACROSS the coil's terminal.
This is what the math says. And this is what the physics says. The amount of fuel per passenger when you go from LA to NY is different for different paths: if your path goes through Chicago it's one number; if you go through Lima, Peru, it's another.
Apparently this simple concept is inconceivable to KVLers.
jesuscf:
--- Quote from: Sredni on January 13, 2022, 10:41:12 pm ---In my world they are all identical and zero, if we use perfect conductors. In the real world they are equal to the current flowing in the ring times the resistance of the length of the arc, whatever that maybe. I can easily calculate their value no matter how the ring is shaped and placed.
--- End quote ---
I see. I have nothing to discuss with you then.
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