An interesting question from Veritasium on YouTube

In summary, the conversation on Veritasium's YouTube channel discussed the possibility of sending a signal faster than the speed of light through a circuit with very long transmission lines. The participants debated various parameters and components of the circuit, such as the voltage of the battery and the impedance of the transmission line, and questioned the practicality and feasibility of such a circuit. The concept of capacitance and its role in the circuit was also brought up, and one participant even shared a simulation of the circuit. Ultimately, it was concluded that the theory of relativity still holds true and signals cannot travel faster than the speed of light.
  • #141
vanhees71 said:
It's not along the wire and not via the electron fluid but via the field, as nicely demonstrated by the simulations shown in the movie and also verified by measuring the signal of the transient state.
But would you agree that the electrons have a longitudinal motion, oscillatory for AC, in response to the fields?
 
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  • #142
Sure, they make up the current.
 
  • #143
vanhees71 said:
Indeed, one should show this movie to all the "physics pedagogues" still advocating a kind of "water-pressure model" of electric circuits, which is completely wrong in many ways, particularly in the discussed issue with how energy is transported from the source ("battery"). It's not along the wire and not via the electron fluid but via the field, as nicely demonstrated by the simulations shown in the movie and also verified by measuring the signal of the transient state.
I expect Veritasium to make a video saying the battery is not the source next. :)
 
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  • #144
bob012345 said:
I expect Veritasium to make a video saying the battery is not the source next. :)
The switch is the source of the wave in a circuit.
 
  • #145
tech99 said:
The switch is the source of the wave in a circuit.
Some people will quibble over the choice of words. The switch triggers the wave, but it is not the source of power. Closing a switch in a wire with no power source, produces nothing.
 
  • #146
anorlunda said:
Some people will quibble over the choice of words. The switch triggers the wave, but it is not the source of power. Closing a switch in a wire with no power source, produces nothing.
Yes, battery at the exchange, dial at the subscriber premises.
 
  • #147
vanhees71 said:
Sure, they make up the current.
So can we say that the electrons execute a longitudinal wave? And can we also say that they do this in response to a longitudinal, rather than transverse, electric wave?
 
  • #148
anorlunda said:
Closing a switch in a wire with no power source, produces nothing.
Tree, forest, no people, ...
 
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  • #149
By changing the voltage sources, or arrangement of the conductors, resistors and insulators, we reconfigure the electric field. Those electric fields are guided by the wires and components of our circuits.

In response to the changing electric field, a current flow is required to redistribute the charge of the circuit capacitance. That current generates a magnetic field, guided by the currents in the wires.

Changes to the electric and magnetic fields constitute a redistribution of energy in the fields. The direction of that energy flow is the (cross) product of the electric and magnetic fields, we call it the Poynting vector.

Those EM fields fill the space between the circuit elements, where changes propagate at a speed close to the speed of light. It follows that electrical energy travels to the load through the space surrounding the circuit elements, guided by, but not through, the conductive wires.
 
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  • #150
Baluncore said:
It follows that electrical energy travels to the load through the space surrounding the circuit elements, guided by, but not through, the conductive wires.

That is the well stated answer as reiterated several different times recently I thought we had all figured this out.

tech99 said:
So can we say that the electrons execute a longitudinal wave? And can we also say that they do this in response to a longitudinal, rather than transverse, electric wave?
Please let's not play twenty questions. If you have a point, please make it completely.
 
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  • #151
Old thread closed temporarily for review by the Mentors...
 
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  • #152
hutchphd said:
That is the well stated answer as reiterated several different times recently I thought we had all figured this out.
Exactly. Thread will remain closed. Thanks everybody for an interesting thread.
 
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