The Big Misconception About Electricity

SpongeboB Sinewave

Solar Enthusiast
They make the assumption that "on" means any none voltage across the light bulb's terminal. It takes nanoseconds for the RF/EMF wave + capacitance to across the 1 meter air gap.

It'll take 1 second for DC steady state voltage to reach the bulb and turn in on in the way we understand it.

Nanoseconds is technically correct by the definition of when the light bulb turns on but it's just dumb and misleading. Again, this video is the opposite of educational.
Okay thank you! That makes sense. Now if this is a incandescent light bulb, you are not going to see it turn on in that three nanoseconds in reality, even if the wire is superconducting.

So what you say makes perfect sense but The one /c answer is completely misleading not just partly misleading and my mind.

The c constant could then be the velocity of light or capacitance. If as you say it has to do with the capacitance of the gap between the wires then it was a trick question in my mind
 

Posplayr

Solar Enthusiast
Well I'm (kind of) corrected. I did a steady state dc analysis. He did a transient analysis. I wish he used real values that represent the 1 m apart capacitance. I'm not sure the initial transient would have turned the light on.
This is a classic of example of "Those that can Do (EEVblog) ; those that can't teach(Veritasium)!

Based on the EEVblog's video, the answer to the question posed(by Veritasium) basically has nothing to do with the video (i.e. Poynting vectors and field theory) that describes the supposed problem. It is all distraction.

The light comes on instantly due to the rise time of the instantaneous change in voltage across the local 1 meter spaced wire parasitic capacitance.
 
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FilterGuy

What, me worry?
Wow.... I never expected the video to spark such an interesting debate!!!

A couple of observations:

1) There are many places in physics where a model works perfectly well in common applications but breaks down at the extremes.
  • The Newtonian gravity model works perfectly well for almost all we do, but completely misses the mark of Einsteins equations.
  • E=IR and P=IV work perfectly well for what we typically do, but it may not describe what is going on at the electromagnetic fields and waves level..
2) There can be multiple models that accurately describe the same physical event.
  • Light can be accurately described as both photons and waves.
  • There are two very different descriptions of what makes an airplane fly. They both match all empirical tests yet, physicists can't decide which is 'correct'
 

robby

Solar Addict
That video just causes a whole lot of confusion over nothing.
Now that someone mentioned that it is really 1m/C it all becomes very clear that he is talking about the Capacitance between both of the lines and the Transient impedance that is created at the moment the switch is turned on. Assuming those wires are 1 meter apart.
If someone is really thinking that in the real world the bulb will be shinning brightly in a few nanosecond or whatever it works out to be they are going to be disappointed. These kinds of Transients can be ignored for the most part when working with DC and would only become an issue in high frequency work. Misleading again because he is using a battery in the example.
 

Cal

Solar Addict
If someone is really thinking that in the real world the bulb will be shinning brightly in a few nanosecond or whatever it works out to be they are going to be disappointed. These kinds of Transients can be ignored for the most part when working with DC and would only become an issue in high frequency work. Misleading again because he is using a battery in the example.

That's been my opinion. The initial turn-on transient won't have enough power to turn on the light. The video is quite disingenuous because when he closes the light switch the light turns on "instantaneously" and remains on. This is absolutely wrong.

After viewing the video again I need to make a correction to my steady state calculation. I used a wire distance of 300,000 km. The actual round trip wire distance is 4 * 300,000 km. The inductance of this wire is 6.27 kH. The wire in conjunction with the resistive light acts as a low pass filter. The time constant of the low pass filter is L/R. If the light has 10 ohm resistance, the time constant is 6.27 kH / 10 ohm = 627 seconds, or about 10 minutes. Once the switch is closed, voltage at the light slowly increases. After 10 minutes the voltage is 63% of battery voltage. The light would be still dimmed.

The guy also mentioned the wire has no resistance. That's extremely important for this model. He's relying on the 2 * 300,000 km dual wire length to be a perfect capacitor. Even without wire resistance, the cable still has inductance.

His ground rules are:
1. no wire resistance
2. no wire inductance
3. being 1 m apart, the wire act as a giant (perfect) capacitor

The turn-on transient turns the light on.
 

Posplayr

Solar Enthusiast
That's been my opinion. The initial turn-on transient won't have enough power to turn on the light. The video is quite disingenuous because when he closes the light switch the light turns on "instantaneously" and remains on. This is absolutely wrong.
You have a far higher chance of lighting a bulb using static electrical charge (2-4Kv human model for ESD) and although I have seen blue ESD sparks there is not enough energy to heat an incandescent bulb filament.

This is the reason for his assumption that one election is enough to light the bulb forever presumably. And then he threatens to actually go test the theory in the desert so he has room to unroll these giant roles of wire. The whole thing would appear to be purposefully constructed to generate clicks. In other words, the knowing played a game of sleight of hand to create a controversial statement about something that ultimately is a fabrication.
 
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solarsimon

Solar Enthusiast
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My brain is now officially melted. And I got the question wrong.
Please tell me that all those (mainly Indian) videos are now true and all I need to power my house is some long cables, lossy rubber belts, a flywheel and a well trained hamster called Elvis.
 

SpongeboB Sinewave

Solar Enthusiast
They make the assumption that "on" means any none zero voltage across the light bulb's terminals. It takes nanoseconds for the RF/EMF wave + capacitance to cross the 1 meter air gap.

It'll take 1 second for DC steady state voltage to reach the bulb and turn in on in the way we understand it.

Nanoseconds is technically correct by the definition of when the light bulb turns on but it's just dumb and misleading. Again, this video is the opposite of educational.

Yes ! I would call this kind of a trick question actually. Of course we all understand that a capacitor will allow a short pulse of current through the light bulb ! Now, had he had the battery and switch on one end of the pair of wires and the light bulb on the other end of this wire pair, the results would have been different and the explanation would have been different. Poynting vectors would still have been used in the explanation(s).

At my old-ish age, trick-ish questions like this make me question whether I am actually sane or not ! :) 😋

Next, do the same problem using a variable voltage supply cranked up slowly. :)
 
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