Velocity of electrons in a wire

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Discussion Overview

The discussion revolves around the concept of electron velocity in a wire, particularly focusing on drift speed and its relationship to electric current. Participants explore how a seemingly slow drift speed can still result in a significant current flow due to the large number of free electrons present in a typical wire.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that while electrons move in various directions, applying a voltage causes some to drift in the direction of the voltage, leading to a drift speed.
  • Another participant emphasizes the abundance of free electrons in a wire, questioning how a current of 1 ampere can be achieved despite the slow drift speed.
  • Several participants highlight that the large number of electrons (approximately 8.5 * 10^28) in a wire allows for a high current flow, despite the slow drift velocity of individual electrons.
  • One participant compares the behavior of electrons in a wire to a toy demonstrating how internal components can move minimally while still allowing for a quick overall effect.
  • A later reply affirms the previous points about the relationship between drift speed and current flow, reiterating the significance of the number of electrons involved.

Areas of Agreement / Disagreement

Participants generally agree on the relationship between drift speed and the number of electrons contributing to current flow, but the discussion remains exploratory without a formal resolution of all underlying concepts.

Contextual Notes

The discussion does not resolve the complexities of how drift speed and electron density quantitatively relate to current, nor does it clarify the assumptions behind the stated values and comparisons.

Who May Find This Useful

This discussion may be useful for individuals interested in understanding electric current, drift speed, and the behavior of electrons in conductive materials, particularly in educational or exploratory contexts related to physics and electrical engineering.

moment1337
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Electrons are moving in moves in all sorts of directions, causing the net electric charge to cancel out. But, when you apply a voltage, there's a small amount of electrons that will move towards the direction in the direction of the voltage. This is called the drift speed. Am I right? I read that the drift speed usually is 1/10000 of a second. How can you then obtain a current of 1 ampere, when 6.25*10^18 electrons has to move past a single point in one second, when the drift speed of the charge is that slow?
 
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moment1337 said:
a small amount of electrons
There are lots of free electrons in a typical wire.

moment1337 said:
How can you then obtain a current of 1 ampere, when 6.25*10^18 electrons has to move past a single point in one second, when the drift speed of the charge is that slow?
Lots of electrons!

See: Microscopic View of Electric Current
 
Oh I see now. So the drift velocity of a single electron might be very slow, but because there are 8.5 * 10^28 electrons in a wire point of the wire, you still can get a pretty high current flow?
 
moment1337 said:
Oh I see now. So the drift velocity of a single electron might be very slow, but because there are 8.5 * 10^28 electrons in a wire point of the wire, you still can get a pretty high current flow?

200px-Newtons_cradle_animation_book_2.gif

Have you seen this toy? It demonstrates the concept nicely. The time from an ball enters the ball chain to the end ball bouncing out is very short - but the internal balls (like the electrons in the wire) hardly move at all.
 
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Svein said:
200px-Newtons_cradle_animation_book_2.gif

Have you seen this toy? It demonstrates the concept nicely. The time from an ball enters the ball chain to the end ball bouncing out is very short - but the internal balls (like the electrons in the wire) hardly move at all.

Bravo Svein. This question comes up frequently on PF. That little video you posted explains it better than 10,000 words.
 
moment1337 said:
Oh I see now. So the drift velocity of a single electron might be very slow, but because there are 8.5 * 10^28 electrons in a wire point of the wire, you still can get a pretty high current flow?
Exactly.
 

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