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Voltage and Current

Anonymous Fri 26 Nov 22:40:29 2021 No.13894215 View Reply Original Report

Quoted By: >>13894220 >>13894229 >>13894319 >>13894389 >>13894491 >>13894769 >>13894776 >>13894789 >>13895183 >>13896511

Question stolen from Veritasium youtube.com/watch?v=bHIhgxav9LY

Closing this circuit via switch, how long would it take the lamp to light? Light can travel 300,000,000 meters a second.

Red lead is 300,000,000 meters long
Green lead is 300,000,000 long

They are magical lines with no resistance, no noise or any other interference.

I have a stupid guess which I will share in a bit

Anonymous

Anonymous Fri 26 Nov 2021 22:41:33 No.13894220 Report

Quoted By: >>13894233

>>13894215
OP, whose fridge are you putting this up on later?

Anonymous

Anonymous Fri 26 Nov 2021 22:43:11 No.13894229 Report

Quoted By: >>13894240

>>13894215
light isn't electricity retard

Anonymous

Anonymous Fri 26 Nov 2021 22:43:43 No.13894233 Report

Quoted By:

>>13894220
I’m going to put this up on mom’s fridge later.

>Mom I copied a drawing from YouTube and redrew it

I’m more interested in the answer to the question. I did not author the question, and claim no credit for that.

Anonymous

Anonymous Fri 26 Nov 2021 22:45:18 No.13894240 Report

Quoted By:

>>13894229

Well do you have an answer or a guess?

Anonymous

Anonymous Fri 26 Nov 2021 23:01:40 No.13894304 Report

Quoted By: >>13894321

OP here. My guess?

3 seconds for lamp to light.

2 seconds for Voltage to travel from the positive Terminal to the negative terminal.

1 second for current to travel from negative terminal to energize the lamp.

Anonymous

Anonymous Fri 26 Nov 2021 23:04:30 No.13894319 Report

Quoted By: >>13894329

>>13894215
milliseconds, search electro magnetic fields

Anonymous

Anonymous Fri 26 Nov 2021 23:05:39 No.13894321 Report

Quoted By: >>13894329 >>13894901

>>13894304
voltage and current don't travel, they move vigorously back and forth

Anonymous

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Anonymous Fri 26 Nov 2021 23:06:56 No.13894329 Report

Quoted By: >>13894368

>>13894319

Lol ok.

>>13894321

We are talking about DIRECT CURRENT. check my shitty drawing. It says DC.

Anonymous

Anonymous Fri 26 Nov 2021 23:14:53 No.13894368 Report

Quoted By: >>13894386 >>13894885

>>13894329
yes, it is all to do with electro magnet fields and nothing to do with electrons be it ac or dc or w/e current constant or direct, pulse or w/e.

Anonymous

Anonymous Fri 26 Nov 2021 23:18:48 No.13894386 Report

Quoted By: >>13894393

>>13894368
Well my claim is that current will travel at C given no resistance or outside interference.

Voltage doesn’t travel according to almost anyone you ask. But I think the force DOES travel. How can you start current without voltage arriving at the negative terminal - allowing current to flow to the load???

Anonymous

Anonymous Fri 26 Nov 2021 23:20:35 No.13894389 Report

Quoted By: >>13894391

>>13894215
100% of the energy supplied will be lost as heat due to electrical resistance.

Anonymous

Anonymous Fri 26 Nov 2021 23:22:49 No.13894391 Report

Quoted By: >>13895220

>>13894389
Ya but you’ll have a pretty lamp that’s well lit.

Remember the lines are magic. The lamp is the load and of course the energy exits the circuit via heat through the lamp.

Anonymous

Anonymous Fri 26 Nov 2021 23:24:23 No.13894393 Report

Quoted By: >>13894400

>>13894386
>current
electrons or ions
does it really travel or just move back and forth?

Anonymous

Anonymous Fri 26 Nov 2021 23:27:08 No.13894400 Report

Quoted By: >>13894431

>>13894393
I don’t know. Are dominoes falling down individually or is there a force that travels through every domino?

I think there is a force traveling through every domino.

Anonymous

Anonymous Fri 26 Nov 2021 23:35:43 No.13894431 Report

Quoted By: >>13894434 >>13894885

>>13894400
again, its the electro magnetic force that gives you 1/c

Anonymous

Anonymous Fri 26 Nov 2021 23:37:52 No.13894434 Report

Quoted By: >>13894445

>>13894431
>1/c

Which formula are you using? And for what purpose?

Anonymous

Anonymous Fri 26 Nov 2021 23:42:19 No.13894445 Report

Quoted By: >>13894446

>>13894434
doesn't matter, milliseconds is your answer even if your wire is 300 miles long.

Anonymous

Anonymous Fri 26 Nov 2021 23:43:16 No.13894446 Report

Quoted By:

>>13894445
Yeah. 3000 milliseconds. You are correct

Anonymous

Anonymous Sat 27 Nov 2021 00:00:47 No.13894491 Report

Quoted By: >>13894496 >>13894885 >>13896801

>>13894215
is the veritasium video a joke, or just cheating on the explanation? there would be some EM field from the battery to the lamp in 1/c seconds, but I really doubt the lamp would fully light after only 1/c seconds. if that happened, it would imply that somehow the information about the connection between the power source and the lamp travels directly, independently of the wires, but... it still would need the wires. am I wrong here?

Anonymous

Anonymous Sat 27 Nov 2021 00:03:20 No.13894496 Report

Quoted By: >>13894524 >>13894532

>>13894491
>there would be some EM field
*traveling from the battery to the lamp in 1/c seconds
what I meant is, it seems to be a dumb, tricky question to explain EM fields, but not really a good one to explain the whole "electrical power" problem

Anonymous

Anonymous Sat 27 Nov 2021 00:15:13 No.13894524 Report

Quoted By: >>13894947

>>13894496
Just for thought. How long does it take for current to reach a load from the terminal???

Current is traveling from the - terminal to the load lamp.

Anonymous

Anonymous Sat 27 Nov 2021 00:17:57 No.13894532 Report

Quoted By: >>13894549 >>13894947

>>13894496
Also notice that there is NO CURRENT when the circuit is open. No current and no power.

There is only current when the circuit is closed. The leads complete the circuit and ohms law.

V
I R

Anonymous

Anonymous Sat 27 Nov 2021 00:22:51 No.13894549 Report

Quoted By:

>>13894532
Sorry this is incorrect. Ohms law only applies to purely resistive circuits.

But it applies to open and closed circuits. How long does it take current to flow from ground to the load resistor? Nearly the speed of light. Wire resistance and outside interference will down current some what

Anonymous

Anonymous Sat 27 Nov 2021 01:39:39 No.13894769 Report

Quoted By:

>>13894215
your question is ill-posed. Just knowing how long a lead is not sufficient. If fact the video from Ve is similarly ill-posed, but still atleast gives the distance from the power source to the load. In reality a switch isn't DC it has an infinity of frequency components theoretically. These frequency components will propagate down the lines, but only if the impedances are matched.

Anonymous

Anonymous Sat 27 Nov 2021 01:40:50 No.13894776 Report

Quoted By:

>>13894215
>veritasium
go back

Anonymous

Anonymous Sat 27 Nov 2021 01:46:51 No.13894789 Report

Quoted By: >>13894941

>>13894215
I haven't watched the video and if you're asking the question then the video doesn't answer it.

The simple way of putting it is that the lamp isn't really lit by electrons passing through it, just by electrons moving around *within* the lamp.
Our lights turn on because of a magnetic field that is set up within the circuit, not because electrons near the voltage source moved very fast. In fact, the mean free path of electrons through copper wire is extremely slow--something like 0.05 m/s or something. So, the light will turn on once the magnetic field propagates through the system, that is to say that you could have a coil billions upon billions of meters long and the lamp could be sitting right next to the coil and it will turn on immediately, having (almost) nothing to do with electrons passing through the extremely long coil

Anonymous

Anonymous Sat 27 Nov 2021 02:19:11 No.13894885 Report

Quoted By: >>13894947 >>13895136 >>13895231

>>13894368
This is just plain wrong. The premise of Poynting vectors is not that the moving electrons are irrelevant, but rather that the energy transfer occurs via fields. For Poynting vectors to exist you need a nonzero magnetic field orthogonal to the electric field, but the source of this nonzero magnetic field is, in a conductor, the moving charges (see Maxwell's fourth equation describing the curl of the magnetic field). This equation also explains why Veritasium's wire situation *temporarily* works, as there was displacement current due to capacitive coupling between the parallel wires. Once this capacitance is charged during DC or low frequency AC the current must propagate all around the loop (via moving charges).

>>13894431
>>13894491
Are these a joke? Veritasium's "1/c" is actually (1m/c) because of the 1 meter distance between the two parallel wires creating transient displacement current. In OPs case there is no capacitive coupling and so the electric field must propagate all of the way along the wires.

Anonymous

Anonymous Sat 27 Nov 2021 02:23:54 No.13894901 Report

Quoted By:

>>13894321
travel and move are the same thing.
and V and I do neither. it is the electrons that move. or travel.

Anonymous

Anonymous Sat 27 Nov 2021 02:37:20 No.13894941 Report

Quoted By: >>13897761

>>13894789
>that is to say that you could have a coil billions upon billions of meters long and the lamp could be sitting right next to the coil and it will turn on immediately, having (almost) nothing to do with electrons passing through the extremely long coil
False, such an extremely long coil would have an extremely high inductance, taking quite a while for the magnetic field to build up. And just like in Veritasium's example, there will be capacitive coupling between the loops of the coil and the loops in front of them, allow for displacement current to take a shorter path.

In basic circuits people are usually only dealing with the first half of Maxwell's equation (Ampere's law), however in many real world examples Maxwell's addition (displacement current) must be considered. Veritasium and you guys are contriving examples that involve displacement current and then trying to pretend Ampere's law is irrelevant, when in fact they are *both* relevant depending on the situation.

Anonymous

Anonymous Sat 27 Nov 2021 02:38:56 No.13894947 Report

Quoted By:

>>13894524
current should take 1s or more to travel, right?

>>13894532
but that doesn't mean the current (and the fields created by it) would travel in 1/c seconds throught the cable, does it?

>>13894885
>Are these a joke?
my question is not a joke.

>Veritasium's "1/c" is actually (1m/c) because of the 1 meter distance between the two parallel wires creating transient displacement current
I don't know much about the topic, but if I'm not mistaken, there are two EM "waves" being generated in the Veritasium case: one appears when current starts to travel (at 1m of distance), one generated by the current itself when traveling through the lamp (at 0 distance). am I wrong?

Anonymous

Anonymous Sat 27 Nov 2021 03:10:18 No.13895023 Report

Quoted By: >>13895090

Unrelated opinion, I think OP is between 40 and 50 years old due to his hand writing.

Anonymous

Anonymous Sat 27 Nov 2021 03:34:26 No.13895090 Report

Quoted By: >>13895177

>>13895023
OP is 40. You are corrrect

Anonymous

Anonymous Sat 27 Nov 2021 03:57:03 No.13895136 Report

Quoted By: >>13895155

>>13894885
Ee grad here. This man speaks the truth it’s basic transmission line theory shit. Veritasium is just clickbaiting retarded normies nothing new move on

Anonymous

Anonymous Sat 27 Nov 2021 04:04:57 No.13895155 Report

Quoted By:

>>13895136

Question: there is no current through the circuit while it is open, correct? Once the switch closes the circuit, what happens???

Does it not take time for current to flow from ground (neg terminal) to the load lamp once the circuit is closed? Also, does voltage travel from the positive terminal, through the load, to the ground terminal? Is Voltage an “instantaneous” force? I don’t believe it is.

Anonymous

Anonymous Sat 27 Nov 2021 04:13:28 No.13895177 Report

Quoted By:

>>13895090
Ha! You broke into cursive several times. I knew it!

Anonymous

Anonymous Sat 27 Nov 2021 04:15:45 No.13895183 Report

Quoted By:

>>13894215
it'd take one second to light up

Anonymous

Anonymous Sat 27 Nov 2021 04:31:02 No.13895220 Report

Quoted By: >>13895242

>>13894391
No, you will not transmit 120v of anything 300,000 km long. The lamp won’t be lit.

Anonymous

Anonymous Sat 27 Nov 2021 04:33:09 No.13895231 Report

Quoted By: >>13895239 >>13897383

>>13894885
Can we please stop making this shit so misleading.

Vertiasium is a fag for this latest video because he left out a ton of EE on purpose to make it seem like energy is magic. There are two things not being directly stated that affect this result. One is that we're giving resistance a free pass and two is that actual energy values aren't being considered, just absolute latencies.

So the thought experiment asks us, when will the energy reach the bulb? But what is the energy that actually matters? Is it the emitted EMF from current passing through a conductor? Or is it the current itself? See its just a technicality in the video, yes the emitted EMF reaches the bulb before the current does. But any EMFs reaching the bulb will be extremely weak and otherwise unnoticeable.

To bring this into real life just know all energized wires emit an EMF, even powerlines. But nobody would consider this EMF to be the main portion of energy actually being transmitted. See, current flowing through a wire actually creates that field; the field is NOT the flow of energy. It can essentially be seen as a side product of the flow, even if everything is in proportion.

Anonymous

Anonymous Sat 27 Nov 2021 04:36:29 No.13895239 Report

Quoted By: >>13897383

>>13895231
there we go, I was 2 of those replies he was calling out. thank you for putting it into words that I couldn't.
/science settled

Anonymous

Anonymous Sat 27 Nov 2021 04:37:15 No.13895242 Report

Quoted By:

>>13895220

It’s a magic lead with no resistance. Or if you wish to use ohm’s law, you could say the + - leads each have 15 ohms.

Because ohm’s law states you can’t have Voltage with zero resistance.

120V = I (4A) x R (0ohms) doesn’t really make sense.

But 120V = 4A x 30 ohms

Anonymous

Anonymous Sat 27 Nov 2021 13:10:02 No.13896511 Report

Quoted By:

>>13894215
See my reply here

>>13896481

The short answer is Derek from Veritasium is a fucking retard, and his video is completely wrong. The Poynting vector gives the directional energy flux for far field EM waves, ie light, x rays, radio waves, etc. It does not apply to the reactive near field, since the near field does not propagate like the far field does. Most of the near field collapses back into the source and is reliant on it, it does not propagate outwards independent of the source like the far field. The bulb would light up initially due to the capacitance between the conducting wires. EEV blog has a video where he uses a simulated transmission like that shows these parasitic capacitances. He does however then go on to say he agrees with Veritasium, which was disappointing to hear.

Anonymous

Anonymous Sat 27 Nov 2021 15:11:10 No.13896801 Report

Quoted By: >>13897383

>>13894491
Yeah, he fucked up.
Power going to the light in 1/c seconds is due to a changing magnetic field as the battery starts current flowing. It would be tiny, and dependent on the physical arrangement of the lamp and conductors.

Consider what happens when the switch is turned off. The lamp doesn't immediately turn off because it's fed by electrons (driven by em fields). That current is physically different to the current induced by the changing magnetic flux that can start its influence in separation/c seconds.

He made a big mistake.

Anonymous

Anonymous Sat 27 Nov 2021 18:24:22 No.13897383 Report

Quoted By:

>>13895231
Not sure why it seems like you're calling me out when we agree.

>>13895239
He's calling you out just as much as I was.

>>13896801
Derek's most retarded move was using "1/c". Now every idiot thinks "1/c" is some constant when in reality it only applied in Veritasium's case because the parallel wires were 1 meter apart.

Anonymous

Anonymous Sat 27 Nov 2021 20:25:42 No.13897761 Report

Quoted By:

>>13894941
>False, such an extremely long coil would have an extremely high inductance
You're right, I have no idea why I didn't consider that. Inductance is proportional to the square of the number of coils so yeah, you are correct and I was wrong. I apologize anon-sama

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