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Veritasium "How Electricity Actually Works"
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SandyCox:
A photon is the elementary particle dual of an electromagnetic wave. Light is an electromagnetic wave.
Naej:

--- Quote from: hamster_nz on May 10, 2022, 03:35:09 am ---How is that momentum transferred? When a marble rolls past a stationary one, the stationary one doesn't just start moving. Do the charges have little sticks that the prod each other with?

--- End quote ---

This is, again, a non-physical question.
If you want to imagine that charges water the magnetic field, and magnetic wheat pushes on far-away charges, it works.
If you want to say that God propagates potential and momentum at the speed of light, it works too.
What really matter is: it is, and does so according to Maxwell equations.

--- Quote from: hamster_nz on May 10, 2022, 03:35:09 am ---How does that current and potential get into the middle capacitor? And what what is current times potential, if it isn't energy?

--- End quote ---

So you agree that energy is flowing in wires in the middle capacitor?
For how the potential travels: see above.

--- Quote from: hamster_nz on May 09, 2022, 11:02:33 pm ---For electrostatics, the electric field fill the universe (just like gravity does). And the location of charges in that field define the electric field, just like how the location of masses define the gravitational field.

In a wire, where charges can move freely, changes drift to where they see the local field leading them, like marbles rolling down into a valley under gravity. They don't need to 'know' that there is a battery that is 10cm away to know which way to go, they just mindlessly follow the slope of the local electric field. Exactly like how water finds it's way to the outlet of a lake or dam. And as they move, their location also contributes to the electric field.  Because charges are able to freely move within the wire, and their location defines the electric field, the electric field quickly becomes flat inside conductors when modest currents are flowing. The charges are not dissipating much energy, they are "doing minimal work" in the physics sense (force x distance).

At the edges and outside of the wires, where the charges can't freely move is where all the tension in the electric field occurs - that is where the fields have the most 'slope'. It is on that slope where you can extract energy from the fields. If you release a charge on such a slope it will know which way want to go - a negative charge will head in the "most positive" direction, and a positive charge will head in the "most negative" direction. If you were able to put an extra charge into a wire not much will happen - it will just drift along on the current.

You attach one end of a resistor to a just the positive wire, but leave the other end free. A small amount of charge will flow into it, but very quickly the whole resistor will have an flat electric field, just as flat as the wire. Anywhere you measure with a voltmeter on the either resistor or the wire will measure 0V. The resistor isn't releasing any of the field's energy, just moving where the field's energy is in space.

But when you attach one end of the resistor to a positive wire. and the other end to the negative wire, then you can extract energy from the field. All the semi-mobile charges in the resistor will see the "so many volts per meter" slope of the field and start moving in that direction. Those charges don't need to know how the electric field gets there, just that the field is there, and it has to follow it. This converts electrical energy into momentum of the charge.

Because the slope in the resistor is so high compared to that inside the wire, they really want to move fast. This gives the thermal heating (or light from the light bulb). That energy isn't coming from the electrons moving in the wire, but the slope in the electric field that is through the resistor, that is what accelerates the charge.

The wire supplies a steady supply of low-energy electrons to be accelerated in the resistor, and removes the low energy electrons that appear at the resistor's other end. The charge is accelerated using the energy supplied by the field, not the wire.

All this time, (assuming resistance of the wires is low compared to the resistor the wires) the electric field on the inside of the wires is flat, and the charges in the wire only transfers minimal energy. The wires set the shape of the electric field, and supplies charge, but the energy flows in the fields.

Batteries also change the shape of the electric field. They generate (and try to maintain) an electric field between their terminals. Batteries are sold as X volt batteries. The first thing you care about for a battery is the strength of the electric field it generates between its terminals. The total energy it can supply is a secondary consideration (along with size or cost). When you connect a battery to a wire, because the wire's charges are mobile the electric field around that wire changes to match that of the battery's terminal. And sure, some charge movement is required for this, but if you could look at how much charge moved how far to build up the electric field it is minimal. (That is unless somebody has put a large capacitor in there somewhere...)

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Sounds mostly correct to me. But I don't see how electrons are shoved by the electric field, with a stick perhaps? And how do they 'see' it, with tiny eyes?
And if you care about the strength of the electric field, why are they sold as X volt, instead of Y volt/meter? I think you care more about the potential difference than the electric field strength.
Ah and of course, you say that 'energy is in electron' is false, but with no experimental evidence; so it's your opinion, not a fact.
Naej:

--- Quote from: bsfeechannel on May 10, 2022, 06:02:25 am ---
--- Quote from: Naej on May 09, 2022, 09:21:38 pm ---which explains clearly that it is a theory dictating where energy flows, not experiments.
Much like bsfeechannel, they don't point to experiments, because they cannot.

--- End quote ---

It's theory explaining experiments. That's what a theory is for. I told you several pages ago that the idea that energy was transmitted in wires was already debunked in the 19th century based on experimental data. I even described what experiments they were.

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I must have missed it. Please explain what experiment was done, what was predicted by the S=JV folks, and what was found. (And why Poynting-Heaviside-etc. do not talk about it.)
Also, theories *predict* the result of experiments. You can see this as an 'explanation' if you like but the (main) goal is to have a discrepancy as small as possible between the theoretical result and the practical one.
If you ask questions like *how can charges push on each other?* you will be disappointed.

--- Quote from: bsfeechannel on May 10, 2022, 06:02:25 am ---
--- Quote from: Naej on May 10, 2022, 12:40:24 am ---Mmh I'm not quite sure why you renamed potential energy into 'backpack', but if I were to explain electricity to children, I would consider it. Is potential a forbidden word now?
I'm curious how you see energy moving in vacuum. Is vacuum filling/emptying backpacks too? And giving to electrons/protons?

--- End quote ---

What is remarkable of Derek's experiment is that it tosses in the bin all the alternatives to the Poynting theorem--a kind of discussion that only entertain physicists--especially S=VJ, so cherished by the hydraulic analogy lovers.

--- End quote ---
I guess you're correct, something true is now in the bin for millions of people. How remarkable.
I also wonder how exactly all physicists proposing alternatives to the Poynting theorem never saw Derek's antennae coming in the whole 20th century. They must feel very silly now (no).
TimFox:
"Sounds mostly correct to me. But I don't see how electrons are shoved by the electric field, with a stick perhaps? And how do they 'see' it, with tiny eyes?"

As with other fields discussed in physics, the E-field (in V/m) is defined in terms of the physical force exerted by the field on a physical charge.
(The gravitational field, similarly, is defined in terms of the force exerted by the field on a mass.)
F = qE, where the force F and the field E are vectors, and the charge q is a scalar.
The field from electron #1 at a separation (vector) r is Kq1 r1/r2,
where r1 is the unit vector along the separation vector r, and r is the magnitude (length) of the vector r.
The constant K, in SI (mks) units is 9 x 109 m/F, as can be found in any elementary textbook that uses "rationalized mks units".
Therefore, since the electronic charge qe = 1.6 x 10-19 C for both particles, and each has mass 9.1x10-31 kg, you can calculate the acceleration, remembering Newton's Third Law since if both electrons are free, the mutual repulsion sends both of them in opposite directions in the "lab frame".
With equal charges, one gets the familiar "inverse square" dependence on distance and q1q2 dependence on the charges.
IanB:
The real issue with this thread and others like it, is that the wrong language is being used to discuss the topic under consideration--a natural language, like English.

Such language is too imprecise, and subject to too much misinterpretation.

To be successful, the language used needs instead to be mathematical, such as shown in this video:

(The video even comes with an accidental mistake as a bonus!)


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