How Fast Does Electricity Travel in Long Circuits?

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Discussion Overview

The discussion revolves around the speed of electricity in long electrical circuits, particularly in the context of a circuit that spans a distance of about 10 light seconds. Participants explore whether the light at one end of the circuit would illuminate instantaneously upon activating a switch at the other end, and consider the implications of using superconductors in this scenario.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions whether the light would turn on instantaneously when the switch is thrown, seeking clarification on the time it would take for the signal to travel.
  • Another participant notes that the speed of electricity in a wire is influenced by the wire's physical properties and cannot exceed the speed of light, although it can approach it closely.
  • A different contribution suggests that the time taken for the electrical signal to travel can be approximated by the formula d/c, where d is the length of the transmission line, while emphasizing that actual speeds depend on the geometry and material properties of the transmission lines.

Areas of Agreement / Disagreement

Participants generally agree that the speed of electricity cannot be instantaneous and is limited by the speed of light, but there are nuances regarding the factors that affect the speed, such as material properties and geometry, which remain open for further discussion.

Contextual Notes

There are limitations regarding the assumptions made about the properties of the wire and the surrounding environment, as well as the specific conditions under which superconductors would be used.

Grimble
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Hello folks, this may be a very basic question, but if one has a very long electrical circuit, say about 10 light seconds, with a light at one end and a switch at the other, and the switch is thrown, would the light be lit instantaneously?
If not how long would it take?
And what would the effect be, if the connections were cooled to be super conductors?

Grimble
 
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The speed of electricity along a wire depends strongly on the physical properties of the wire and even the surrounding region. It cannot be "instantaneous" of course- it cannot be faster than c, the speed of light, but it can be close to the speed of light. If you were to do every thing you could to reduce resistance, such as using a "super conductor", you could increase the speed but still not to or beyond,the speed of light.
 
It will take something on the order of d/c where d is the length of the transmission line. Electrical signals travel on the order of the speed of light. What their actual speeds are depend on the geometry and material properties of the transmission lines though.
 
Thank you! That was what I needed to know!

Grimble
 

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