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Just need a clarification here, how the current is produced due to the movement of electrons, in an external circuit,having a very slow drift speed.

Normally in a battery there is high potential terminal and low potential. Using these two terminals the external circuit is closed. Now within the battery the direction of the current flow and the electron flow is opposite to that of the external circuit. If I consider that positive current is flowing from the positive terminal to the negative terminal of the battery through the external circuit then we can say that positive terminal is at higher potential then the negative terminal of the battery.

Now when we are closing the switch of an external circuit, in that case the electrons are moving from negative terminal to positive terminal of the battery, through the external circuit. But we also know that the drift speed is very slow, of the electron. But when we switch on some of the electrical devices, within a fraction of second the device starts working. If drift sped of electron is low, so how the device is working so fast ,(near about the speed of light,I guess), as we know that current flows due to the flow of the electrons.So how it is possible, in spite of electrons are having such a low drift speed ?

Please help me guys !!!!!

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marked as duplicate by RedGrittyBrick, PeterJ, Daniel Grillo, Joe Hass, Matt Young Feb 17 at 15:25

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
oooh, I just had a flashback to Ivor Catt... ivorcatt.co.uk/cattq.htm –  Brian Drummond Feb 17 at 14:57

4 Answers 4

An analogy

Imagine pressing 1 cm ball-bearings into a 10 m long horizontal pipe (1.1cm internal diameter) which is full of identical ball-bearings.

You take 1s to slowly press one new bearing into your end of the pipe

That 1 cm ball bearing travelled at 0.01 m/s

As you press a new ball-bearing in at your end, another ball bearing gets pushed out the far end 10 m away.

That effect travelled at nearly 10m/s

The pressure wave that caused that effect travelled even faster (probably at near the speed of sound in ball-bearing material less some allowance for small gaps between bearings, lateral movements and other messy and irrelevant stuff).

The trouble with analogies

This analogy may help you to think about the different things that are happening at different scales and that they are not related in quite the way you may have thought. Analogies can only go a short way to explaining these subjects.

A Tsunami wave in the ocean, travels at around 800 Km/h (500 MPH) - but the water does't flow that fast.

An electrical signal can travel much faster than electron drift velocity.

Electricity

Electricity is not (simply) a flow of charge carriers. It also involves an electric field. Changes in that field can propagate much faster than charge carriers can move.

Follow-up

throughout the wire, there exist a big number of electron

Throughout all matter, there exist a large number of electrons. This includes air and other materials normally considered insulators - through which there is normally no appreciable current. In metals, the presence of so-called "free electrons" is important, but these are usually only a small proportion of the electrons in the metal.

negative terminal of the battery is having electrons which are having high energy

No, for the purposes of this discussion, they have nearly the same energy as all the other electrons in the wire. The electrons do not carry energy from the battery.

This isn't a useful way to think about electricity. If you wanted to understand the Physics of electricity, Physics.stackexchange would be a good place to do some searches.


See also

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Imagine one electron drifting slowly from the negative pole of your battery into the wire. At nearly the same moment, an electron from the beginning of the wire drifts to a bit further on in the wire, replacing an electron that is (at nearly the same moment) drifting yet further ..... and at the end of the chain an electron from the end of the wire drifts into the positive pole of the battery.

Summary: even though electrons move relatively slow, charge can move fast.

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Normally what I've understood,the wire is having lot of electron(from their atomic structure context). So negative terminal of the battery is having electrons which are having high energy(in terms of negative charge). But rest of the electrons are not having the high energy. So just need to clarify whether these high energetic electrons are repelling the rest of the electrons in the atoms through the entire wire. So that their drift speed might be slow, but they are moving fast due to the electric field produced by the negative terminal of the battery. Am I correct ? Respond Wouter.. –  Harry Potter Feb 17 at 9:43
    
If I am wrong, please provide the needful explanation.... –  Harry Potter Feb 17 at 9:47
    
AFAIK the energy of the electrons has nothing to do with this. –  Wouter van Ooijen Feb 17 at 10:08
    
OK,you are saying that the energy has nothing to do with the electrons,right?Now throughout the wire, there exist a big number of electron, and also in the electrical device.But the electrons at the negative terminal of the battery is having high energy.AFAIK any electrical device is a energy transformation system. So when the switch is on, at that time the high energized electrons are not reached to that electrical device. But the device is producing output, so from where the energy is coming ? So can it be said like this that energy is propagating from one electron to another ? –  Harry Potter Feb 17 at 12:53
1  
Analogies always have a limited use. The 'ball with tubes' analogy explains how charge can travel faster than electrons, which was Harry's question. It should not be used to draw any (other) conclusions. –  Wouter van Ooijen Feb 17 at 14:58

Maybe this analogy will help.

Imagine you and a friend are holding two ends of a very long rope, and you're holding it tight, without any slack. If you pull on the rope, your friend will feel you pull almost instantly. The rope hardly has to move, and could move quite slowly. Similarly, an electron from a battery doesn't have to move very fast or far for the rest of the circuit to "feel" it. The speed of the electron is like the speed of the rope, while the speed at which your friend feels you pull is like the speed at which the electrical circuit works.

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Normally what I've understood,the wire is having lot of electron(from their atomic structure context). So negative terminal of the battery is having electrons which are having high energy(in terms of negative charge). But rest of the electrons are not having the high energy. So just need to clarify whether these high energetic electrons are repelling the rest of the electrons in the atoms through the entire wire. So that their drift speed might be slow, but they are moving fast due to the electric field produced by the negative terminal of the battery. Am I correct ?....Please comment David –  Harry Potter Feb 17 at 9:54


Although the electron velocity is very low, which is propagated almost instantaneously is the electric field. This causes the effect that all the electrons in the wire to start moving simultaneously (almost).

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