Velocity of electrons in a wire

In summary, when a voltage is applied, a small amount of electrons will move towards the direction of the voltage, creating a drift speed. Despite the individual drift velocity of each electron being very slow, the large number of electrons in a wire allows for a high current flow to be achieved. This concept is demonstrated through a toy that shows how a ball entering a ball chain quickly causes the end ball to bounce out, despite the internal balls hardly moving at all.
  • #1
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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  • #2
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
 
  • #3
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?
 
  • #4
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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  • #5
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.
 
  • #6
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.
 

Related to Velocity of electrons in a wire

1. What is the velocity of electrons in a wire?

The velocity of electrons in a wire can vary depending on the material of the wire and the conditions it is in. In general, the average velocity of electrons in a wire is around 1 millimeter per second.

2. How is the velocity of electrons in a wire measured?

The velocity of electrons in a wire is measured using a device called an electron drift tube. This tube uses an electric field to accelerate electrons and then measures the time it takes for them to travel a certain distance, allowing for the calculation of their velocity.

3. Does the diameter of a wire affect the velocity of electrons?

Yes, the diameter of a wire can affect the velocity of electrons. A thinner wire will have a higher resistance, which can cause electrons to move slower. On the other hand, a thicker wire will have a lower resistance, allowing electrons to move faster.

4. Can the velocity of electrons in a wire be changed?

Yes, the velocity of electrons in a wire can be changed by altering the conditions of the wire. For example, increasing the temperature of the wire can cause the atoms to vibrate more, resulting in a higher resistance and slower electron velocity. Additionally, changing the electric field or the material of the wire can also affect the velocity of electrons.

5. How does the velocity of electrons in a wire affect electric current?

The velocity of electrons in a wire is directly related to the electric current in the wire. As the velocity of electrons increases, so does the electric current. This is because a higher velocity means more electrons are passing through a point in the wire per unit of time, resulting in a higher electric current.

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