Is the Speed of Electricity Affected by the Length of the Wire?

In summary: That is correct.If you do not yet understand transmission line theory, then your opinion is just that, an opinion. When I analyse the circuit, I form a more rational opinion.And Dr. Muller (aka Veritasium) is trained as an educator which I believe he does extraordinarilly well in this context.
  • #1
John Mcrain
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300 000km connect light bulb and battery.
I would say 1sec is need from I turn on switch to light start lighting.

This video say it is 1m/c...Is this video wrong?
Do electron travels thorugh wire, if 300 000km wire is connected to bulb ,why electricitly travel through space only 1m??

 
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  • #2
Electrons are indistinguishable particles so the question is not really about this or that electron. They are constrained to the wire, but the energy is in the fields. Yes Veritasium is pretty much correct.
 
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  • #3
hutchphd said:
Yes Veritasium is pretty much correct.
So it is not important how long are wires, its only importnat distance between bulb and battery?
this sound crazy
 
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  • #4
Sorry.

Black holes sound normal?
 
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  • #5
hutchphd said:
Yes Veritasium is pretty much correct.
Dont agree with answer 1/c, this is trick question,because he said any amount of energy/ current will turn on light bulb..
If any current will turn on light,then yes he is right...

But this "induced current" is so low, it is not enough to trigger light...so answer 1m/c is wrong, correct answer is 1sec
 
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  • #6
Of course the answer is a little more nuanced but a 300,000km wire makes a pretty damned good antenna. Derek Muller is essentially correct regardless of what you may believe. This has been well covered here before. Please looked at previous posts
 
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  • #7
hutchphd said:
Of course the answer is a little more nuanced but a 300,000km wire makes a pretty damned good antenna. Derek Muller is essentially correct regardless of what you may believe. This has been well covered here before. Please looked at previous posts
Yes he is correct only in a part that small current will travel through bulb at t=1/c, but this small induced current will not turn light ON.

If bulb need aprox voltage of battery(that is ussualy case) then induced current is many billions too small to start the light..
So this is trick question or technicaly undefined question

He must ask question like this; "what is time need to bulb has non zero current?"...then answer is 1m/c..
 
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  • #8
No. Please look it up. Many billions? Actual physics please.
No mas.
 
  • #9
John Mcrain said:
300 000km connect light bulb and battery.
I would say 1sec is need from I turn on switch to light start lighting.
That is because you do not yet understand transmission line theory.

Two parallel wires appear to be a two terminal resistor, with a value determined by the capacitance and the inductance per unit length.
That will be about 500 ohms for each line in the case presented.
That all changes if/when a reflection returns from the far end.
 
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  • #10
I don't think you'll get a better explanation from us than what you will get from Derek's videos. But yes, he is essentially correct. Also, yes, it may seem a little crazy according to your expectations. That happens a lot in the sciences.
 
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  • #12
Baluncore said:
In this discussion, I agree with @Dale opinion : "In order to light up a bulb must have a substantial amount of current through it. It is not designed to do that in response to a small RF signal propagating through free space. Although such a signal exists and would produce some minuscule current, the bulb would not “light up”.

In short ,some non zero current will flow in bulb in time=1/c, but not enough to light up 12V bulb
 
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  • #13
John Mcrain said:
In short ,some non zero current will flow in bulb in time=1/c, but not enough to light up 12V bulb
The current would be more than minuscule.
Where does the Dale quote come from?
For a 12 volt battery, with 300 ohm parallel wire lines, the filament current could be;
12 volts / (2 * 300 ohms) = 20 mA.
That is more than sufficient to light a fine filament.

The battery voltage, light globe power, transmission line impedance, and the time it takes the filament to heat is not specified. That deliberate lack of specifics is designed to get hits, start arguments in the comments, and more subscribers to that YouTube channel, all of which make real dollars.

If you do not yet understand transmission line theory, then your opinion is just that, an opinion. When I analyse the circuit, I form a more rational opinion.
 
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  • #14
And Dr. Muller (aka Veritasium) is trained as an educator which I believe he does extraordinarilly well in this context.
 
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  • #15
If anyone who doubts this has access to an oscilloscope and the basic capability of building up a pulse generator with a 555 timer it can easily be proven what is happening here.
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It is certainly correct that the experiment Veritasium has done is a little loose on specifics but he is correct. We can use a resistor in place of a bulb and watch the voltage on the scope. We can also terminate the end of the transmission line with a resistor that is equivalent to the characteristics impedance of the line. When the switch is thrown, or the pulse transitions for low to high, we will see the pulse across the local resistor and transmission line length will have no effect on the timing.
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Anyone who doubts this and doesn't want to do the experiment there are examples of it on YouTube. I think it's a good way to get acquainted with transmission lines by doing the experiment. Just standing by and saying you don't believe it is foolish. There is a good opportunity here to learn about transmission lines.
 
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