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Veritasium "How Electricity Actually Works"

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TimFox:

--- Quote from: abquke on June 05, 2022, 07:39:49 pm ---Noise voltage across a bare resistor.

--- End quote ---
The simplest model to analyze thermal noise in a resistor is to connect a capacitor in parallel with the resistor (at finite temperature) and measure the random voltage across the circuit with an ideal voltmeter.
The capacitor determines the bandwidth in the ideal circuit.
Drs. Johnson and Nyquist submitted their papers to Physical Review at the same time--it is rumored that Johnson shoved his under the door of the office at Columbia--(grad student rumor).
The two papers were published in the same issue.  See  https://web.stanford.edu/~edwin98/johnson-shot-noise-paper.pdf

abquke:

--- Quote from: TimFox on June 05, 2022, 07:44:12 pm ---
--- Quote from: abquke on June 05, 2022, 07:39:49 pm ---Noise voltage across a bare resistor.

--- End quote ---
The simplest model to analyze thermal noise in a resistor is to connect a capacitor in parallel with the resistor (at finite temperature) and measure the random voltage across the circuit with an ideal voltmeter.
The capacitor determines the bandwidth in the ideal circuit.
Drs. Johnson and Nyquist submitted their papers to Physical Review at the same time--it is rumored that Johnson shoved his under the door of the office at Columbia--(grad student rumor).
The two papers were published in the same issue.  See  https://web.stanford.edu/~edwin98/johnson-shot-noise-paper.pdf

--- End quote ---

Exactly. A function of the bandwidth of the measurement and the absolute temperature of the resistance. So. What's the explanation that isn't elections bouncing around?

TimFox:

--- Quote from: abquke on June 05, 2022, 07:47:47 pm ---
--- Quote from: TimFox on June 05, 2022, 07:44:12 pm ---
--- Quote from: abquke on June 05, 2022, 07:39:49 pm ---Noise voltage across a bare resistor.

--- End quote ---
The simplest model to analyze thermal noise in a resistor is to connect a capacitor in parallel with the resistor (at finite temperature) and measure the random voltage across the circuit with an ideal voltmeter.
The capacitor determines the bandwidth in the ideal circuit.
Drs. Johnson and Nyquist submitted their papers to Physical Review at the same time--it is rumored that Johnson shoved his under the door of the office at Columbia--(grad student rumor).
The two papers were published in the same issue.  See  https://web.stanford.edu/~edwin98/johnson-shot-noise-paper.pdf

--- End quote ---

Exactly. A function of the bandwidth of the measurement and the absolute temperature of the resistance. So. What's the explanation that isn't elections bouncing around?

--- End quote ---

"Elections"--nice Freudian slip!

abquke:
 :-DD

Yeah whoops.

Naej:

--- Quote from: Terry Bites on June 05, 2022, 04:55:01 pm ---Some time back Dave pointed out that for most practical engineers it doesn’t matter. I'd agree with that. But it may or may not matter, it depends on the situation. It matters very much to ic designers and semiconductor physicists.

--- End quote ---
No it never matter.

--- Quote from: TimFox on June 05, 2022, 05:35:02 pm ---Yes, that which we call Ohm's Law is a result of the scattering of electrons by lots of things in a conductor, so that they do not achieve a high velocity from the voltage gradient along the wire.
An example calculation in  https://www.macmillanlearning.com/studentresources/college/physics/tiplermodernphysics6e/classial_concept_review/chapter_10_ccr_10_mean_free_path.pdf   gives a mean free path between scattering events for electrons in copper as 0.39 nm.

--- End quote ---
This is completely incorrect.
https://homepages.rpi.edu/~galld/publications/PDF-files/Gall-116.pdf
Indicates 39.9 nm.
He assumed that electrons scatters with atoms, while they scatter with phonons.

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