Veritasium "How Electricity Actually Works"

[TimFox]

The elementary features I was taught in the first week of electronics 101 were that you can't change the voltage across a capacitor instantaneously, and you can't change the current through an inductor instantaneously.
Analysis of most simple AC and pulse circuits can start from this, and then introduce the finite resistances and time constants.

Yes that will be basic introduction to have some roule to memorize. But the reason voltage cannot change instantaneously across a capacitor is because energy will be going in the capacitor and stored.
Same thing with inductor where energy is also stored.
All energy that went in except for the amount that was lost in the process as heat will come out of this energy storage devices.
So there is no electrical enenergy that pases trough a capacitor.
Electrical energy is the integral of electrical power over time.  To have power you need to have a current different from zero and you can not have current through a dielectric like plastic or air.

Actually, the point behind the circuit rule that voltage across a capacitor cannot change instantaneously is that it would require infinite current.  Similarly, infinite voltage for the inductor.

[electrodacus]

No, it doesn't matter. We are not interested in the how at this point, only whether it does or not. If there are electrons magically jumping the gap that's fine. It's also fine if they don't. All we need to agree on is that energy is provided on one side, consumed on the other, and there is significant clear air between.

Are you happy agreed with that?

It does matter if you want to claim that energy flows outside the wires.
This is the main point of the entire discussion.
Electrons flow in to wire but do not jump that gap and since electron flow is electrical current and electrical current multiplied with voltage is power and power integrated over time is energy it means energy flows only in wire.

[PlainName]

No, it doesn't matter. We are not interested in the how at this point, only whether it does or not. If there are electrons magically jumping the gap that's fine. It's also fine if they don't. All we need to agree on is that energy is provided on one side, consumed on the other, and there is significant clear air between.

Are you happy agreed with that?

It does matter if you want to claim that energy flows outside the wires.
This is the main point of the entire discussion.
Electrons flow in to wire but do not jump that gap and since electron flow is electrical current and electrical current multiplied with voltage is power and power integrated over time is energy it means energy flows only in wire.

See, this is the problem. You just won't agree with a simple thing without going off on one about something else. Not even a simple fact that is indisputable - you just can't cope with saying, "Yes, OK, that is how it is".

Which of those facts are you disputing? The energy source, the energy sink, or the clear air? Presumably it's the air, but that's actually how it is! Are you going to say the video was photoshopped or something, and that your capacitor calculator (which you chose) is lying or something else?

So, is there or is there not a 1m air gap between the energy source and the energy consumer? Just a straight yes or no, please.

[HuronKing]

I've been reading this discussion and I'm intrigued that pages and pages have gone by and the two words - "displacement current" haven't been mentioned (if they have I missed it!).

If one thinks currents only exist where charge flows, then one would be taking issue with Maxwells Eqs:
https://en.wikipedia.org/wiki/Displacement_current

[electrodacus]

See, this is the problem. You just won't agree with a simple thing without going off on one about something else. Not even a simple fact that is indisputable - you just can't cope with saying, "Yes, OK, that is how it is".

Which of those facts are you disputing? The energy source, the energy sink, or the clear air? Presumably it's the air, but that's actually how it is! Are you going to say the video was photoshopped or something, and that your capacitor calculator (which you chose) is lying or something else?

So, is there or is there not a 1m air gap between the energy source and the energy consumer? Just a straight yes or no, please.

The problem is yours as you fail to acknowledge the real question.
Does the energy travels outside the wires ? so trough that 1m air gap.
If you answer with yes then you need to show how electrons travel from one wire to the other trough that 1m gap.
If no electrons travel through that 1m air gap then no energy travels through that gap.

So it is not me that needs to prove anything it is you that need to prove that electrons travel outside the wire in Derek's experiment.
The experiment was properly done and the results are not disputed here. What it is disputed is the wrong conclusion Derek got from those results.

[electrodacus]

I've been reading this discussion and I'm intrigued that pages and pages have gone by and the two words - "displacement current" haven't been mentioned (if they have I missed it!).

If one thinks currents only exist where charge flows, then one would be taking issue with Maxwells Eqs:
https://en.wikipedia.org/wiki/Displacement_current

You will need to understand Maxwell's equations to understand what they say. They do not say energy flows outside the wires.
Electrons accumulate in to the wires (capacitor plates) and energy is stored that way. The higher the capacitance the more electrons you can push on to plates (conductors/wires).
If you disconnect the battery the potential difference will stay there as stored energy and if you short the two plates electrons will flow through wires from one plate to another discharging the capacitor while energy will end up as heat in the wire as that is the space energy traveled through the wire and not the air space between the plates.

[hamster_nz]

Electrons flow in to wire but do not jump that gap and since electron flow is electrical current and electrical current multiplied with voltage is power and power integrated over time is energy it means energy flows only in wire.

By your own logic, if a wire has 1A flowing it, but almost zero voltage drop across the wire, then integrating the power over time for that wire proves that there is minimal energy in that wire.

If you do the same calculation for the resistor you get reliable results, so why not for a wire? What is so special about it?

And where along the transition between "resistor" and "wire" does this specialness happen? at what resistance or current does your own math become invalid?

[electrodacus]

By your own logic, if a wire has 1A flowing it, but almost zero voltage drop across the wire, then integrating the power over time for that wire proves that there is minimal energy in that wire.

If you do the same calculation for the resistor you get reliable results, so why not for a wire? What is so special about it?

And where along the transition between "resistor" and "wire" does this specialness happen? at what resistance or current does your math become invalid?

A wire is a resistor with lower resistance so there is no difference.
Not quite sure you know what you are asking. Can you be more exact maybe give a proper example with values.

Yes 1A drop on a 0.1Ohm resistor will result in a 0.1V drop across the resistor/wire and thus 0.1W of power lost on the wire as heat.
Same 1A on a 1kOhm wire/resistor will result in 1000V drop thus 1000W of power loss on that wire/resistor.

Where do you see any difference or problem between the two examples ?
 

[hamster_nz]

By your own logic, if a wire has 1A flowing it, but almost zero voltage drop across the wire, then integrating the power over time for that wire proves that there is minimal energy in that wire.

If you do the same calculation for the resistor you get reliable results, so why not for a wire? What is so special about it?

And where along the transition between "resistor" and "wire" does this specialness happen? at what resistance or current does your math become invalid?

A wire is a resistor with lower resistance so there is no difference.
Not quite sure you know what you are asking. Can you be more exact maybe give a proper example with values.

Yes 1A drop on a 0.1Ohm resistor will result in a 0.1V drop across the resistor/wire and thus 0.1W of power lost on the wire as heat.
Same 1A on a 1kOhm wire/resistor will result in 1000V drop thus 1000W of power loss on that wire/resistor.

Where do you see any difference or problem between the two examples ?

None, as you say

electrical current multiplied with voltage is power

Sure, a good wire has 1A flowing in it, and 0V measured across either end, so has 0W

and power integrated over time is energy

Sure, let's integrate 0W for as long as we want.... it's 0 J.

it means energy flows only in wire.

This doesn't follow - the result of your calculation is 0 J.

Well, following your own calculations, there was 0J in that wire.

If it was a 1 ohm resistor with 1A

"electrical current multiplied with voltage is power" - 1A at 1V is 1 W

" and power integrated over time is energy" - let's integrate 1W for a second.... it's 1 J.

Yep, 1J as expected. That checks out.

[electrodacus]

Sure, a good wire has 1A flowing in it, and 0V measured across either end, so has 0W
Sure, let's integrate 0W for as long as we want.... it's 0 J.

good wire ? You mean superconductor.
Yes you can have 1A induced in a superconductor ring and have that 1A flowing forever in there with no energy loss.

A good wire that is not a superconductor will have a resistance low enough that loss is not to high at 1A so that wire will not melt and it is acceptable in your application.
So a resistor is a wire and vice versa thus absolutely no difference between the two.

[PlainName]

See, this is the problem. You just won't agree with a simple thing without going off on one about something else. Not even a simple fact that is indisputable - you just can't cope with saying, "Yes, OK, that is how it is".

Which of those facts are you disputing? The energy source, the energy sink, or the clear air? Presumably it's the air, but that's actually how it is! Are you going to say the video was photoshopped or something, and that your capacitor calculator (which you chose) is lying or something else?

So, is there or is there not a 1m air gap between the energy source and the energy consumer? Just a straight yes or no, please.

The problem is yours as you fail to acknowledge the real question.
Does the energy travels outside the wires ? so trough that 1m air gap.
If you answer with yes then you need to show how electrons travel from one wire to the other trough that 1m gap.
If no electrons travel through that 1m air gap then no energy travels through that gap.

So it is not me that needs to prove anything it is you that need to prove that electrons travel outside the wire in Derek's experiment.
The experiment was properly done and the results are not disputed here. What it is disputed is the wrong conclusion Derek got from those results.

Just one more time: is there or is there not an air gap between the energy source and the energy consumer?

That is the question I am asking. I am not asking the question you would prefer to think I should ask, I am asking this specific and very simple one. Are you afraid to answer it or what? Well, no matter, because this is why we don't get anywhere, and it is why I am done with you.

[electrodacus]

Just one more time: is there or is there not an air gap between the energy source and the energy consumer?

That is the question I am asking. I am not asking the question you would prefer to think I should ask, I am asking this specific and very simple one. Are you afraid to answer it or what? Well, no matter, because this is why we don't get anywhere, and it is why I am done with you.

Yes there is a an air gap.

Now you answer this simple question. Is there any electric current passing through this gap ?
If you say no then you also say no to there is no energy delivered through that gap and all energy travels in wire.

[hamster_nz]

Sure, a good wire has 1A flowing in it, and 0V measured across either end, so has 0W
Sure, let's integrate 0W for as long as we want.... it's 0 J.

good wire ? You mean superconductor.
Yes you can have 1A induced in a superconductor ring and have that 1A flowing forever in there with no energy loss.

A good wire that is not a superconductor will have a resistance low enough that loss is not to high at 1A so that wire will not melt and it is acceptable in your application.
So a resistor is a wire and vice versa thus absolutely no difference between the two.

And yet when you say a wire has 0V measured between its ends you insist that it has energy flowing inside it. You wouldn't say that of a resistor!

[electrodacus]

And yet when you say a wire has 0V measured between its ends you insist that it has energy flowing inside it. You wouldn't say that of a resistor!

Yes energy can travel through a superconductor and there will be no losses. It is a resistor with zero resistance to current flow.
While superconductors seems to be a theoretical ideal case they exist.

[hamster_nz]

And yet when you say a wire has 0V measured between its ends you insist that it has energy flowing inside it. You wouldn't say that of a resistor!

Yes energy can travel through a superconductor and there will be no losses. It is a resistor with zero resistance to current flow.
While superconductors seems to be a theoretical ideal case they exist.

Why do you keep bringing up superconductors? 

What's wrong with copper?

[electrodacus]

Why do you keep bringing up superconductors? 

What's wrong with copper?

You did that when you mentioned a wire with zero resistance.

[hamster_nz]

Why do you keep bringing up superconductors? 

What's wrong with copper?

You did that when you mentioned a wire with zero resistance.

Well let's pick 1m of 2mm copper wire.  That's about about 0.005 ohms.

By your math...

...and since electron flow is electrical current and electrical current multiplied with voltage is power and power integrated over time is energy it means energy flows only in wire.

"electrical current multiplied with voltage is power" - 1A at 0.005V is 0.005 W

" and power integrated over time is energy" - let's integrate 1W for a second.... it's 0.005 J.

So for a 1A in that 1m of 2mm copper wire (a voltage drop of 0.005V), your math calculates that only 0.005 J of energy flowed in that wire during that second.

[electrodacus]

Well let's pick 1m of 2mm copper wire.  That's about about 0.005 ohms.

By your math...



"electrical current multiplied with voltage is power" - 1A at 0.005V is 0.005 W

" and power integrated over time is energy" - let's integrate 1W for a second.... it's 0.005 J.

So for a 1A in that 1m of 2mm copper wire (a voltage drop of 0.005V), your math calculates that only 0.005 J of energy flowed in that wire during that second.

So ? Do you see any problems with that ?
Yes one meter of wire with just 5mOhm resistance will have a voltage drop of just 5mV at 1A.
That 5mJ is the energy that got lost as heat in that wire.
Assuming you had 5V supply the entire circuit should have had 5Ohm for 1A to flow through it so that 1m of wire is just a part of the total circuit.

[SandyCox]

Just one more time: is there or is there not an air gap between the energy source and the energy consumer?

That is the question I am asking. I am not asking the question you would prefer to think I should ask, I am asking this specific and very simple one.[

Now you answer this simple question. Is there any electric current passing through this gap ?
If you say no then you also say no to there is no energy delivered through that gap and all energy travels in wire.

So what is you answer? Yes or No?

Are you sure you're an Engineer and not a Politician?

[SandyCox]

What happens when the electric field isn't conservative? Does current always involve electrons?

In an isolated system the field will be conservative. Electric current will always require some sort of charged particle either electrons or ions. In a wire the electrons will be the ones that move. In a battery the ions will move from one plate to another.

So to transport electrical energy from one plate to another you need electron flow usually in a wire but with very high voltages the electrons can also travel through air but not the case here with 20V and 1m of air.

So electric and magnetic field are conservative in Derek's experiment.

Wrong and wrong. Do you even know what a conservative field is? Have you heard of displacement current?

[PlainName]

Just one more time: is there or is there not an air gap between the energy source and the energy consumer?

That is the question I am asking. I am not asking the question you would prefer to think I should ask, I am asking this specific and very simple one. Are you afraid to answer it or what? Well, no matter, because this is why we don't get anywhere, and it is why I am done with you.

Yes there is a an air gap.

Now you answer this simple question. Is there any electric current passing through this gap ?
If you say no then you also say no to there is no energy delivered through that gap and all energy travels in wire.

Thank you!

Your question: I don't know. That's what we are ultimately trying to determine, but at this point all we know is that there is an energy transfer. What form that energy takes is something to be figured out.

Hopefully you now agree there is energy transfer across that gap. If not, how can one side insert some and the other side use some? We are still not talking about how it transfers, only that there is a transfer.

[hamster_nz]

Assuming you had 5V supply the entire circuit should have had 5Ohm for 1A to flow through it so that 1m of wire is just a part of the total circuit.

So you will agree for the attached schematic, that the instant that SW1 is closed, the initial voltage over R1 will be 5V and 1A will be flowing through it? (and of course it will fall away as the capacitors charge)

And by integrating the V*A over time in the resistor we can find out how much energy has been transferred from the battery to the resistor, because of the connecting wires, switch and capacitors?

How does that energy get there, as you say energy only flows in wires and not through a capacitor?

...and since electron flow is electrical current and electrical current multiplied with voltage is power and power integrated over time is energy it means energy flows only in wire.

[HuronKing]

You will need to understand Maxwell's equations to understand what they say. They do not say energy flows outside the wires.

They absolutely say that. That's what led Maxwell to unify the electric and magnetic fields into electromagnetism... and it's what led Hertz to try transmitting an electrical signal from one radiator to another without any wires whatsoever.

This statement of yours earlier in the thread,

So to transport electrical energy from one plate to another you need electron flow

is absolutely wrong. You seem to believe the only kind of current that exists is conduction current and that only this current transmits energy and the only way for energy to get from one plate to another is if an electron, somehow, crosses the gap. No. No. NO!

Do you know the difference between conduction current and displacement current?

You can start here:
https://youtu.be/SS4tcajTsW8?t=1157

[HuronKing]

Now you answer this simple question. Is there any electric current passing through this gap ?
If you say no then you also say no to there is no energy delivered through that gap and all energy travels in wire.

Don't anyone fall for this question. It's a trick question. He wants you to believe that if conduction current isn't flowing through the gap then no energy is flowing through the gap.

This is against Ampere's Law with Maxwell's addition of Displacement Current. This statement would get an F in any basic physics course.

[HuronKing]

Sorry be posting 3 comments in a row but enough nonsense has been perpetrated here about conduction current being the only way that energy can move from A to B in space. Here is a very simple experiment measuring displacement current as equal to the conduction current but there are NO electrons moving across any gaps whatsoever: