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I'm not an expert and have only a short knowledge of electron. I was looking up the operating principle of lithium-ion batteries and there was something I didn't understand about the way it was expressed, so I'm asking a question.

In most pictures, videos, etc., the way electrons move in a conductor is expressed as if the electrons are moving through the conductor at high speed.

However, as far as I know, the speed of electrons is very slow and the propagation speed of electric fields is very fast.

And I understand that the propagation of the electric field is not created by a single electron moving at high speed, but by electrons in various locations.

In other words, it seems that the free electrons already distributed within the conductor propagate the electric field, not the electrons leaving the electrodes that move quickly through the conductor.

Is my understanding correct? Otherwise, I would appreciate it if you could explain.

Qmechanic
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guss2222
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1 Answers1

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There are three speeds to be considered in a classical interpretation of the conduction process in a metal.

The first is the thermal speed of the free/unbound electrons responsible for the conductions process.
The motion of these electrons can be likened to the molecules in a gas moving around in random directions within the confines of the metal at average speeds of the order of $10^5\,\rm m/s$.

Then there is the speed at which electrons communicate with one another and any external field which is present.
It is the speed at which the information that a switch has been closed in the circuit is conveyed to the rest of the circuit.
That is related to speed of electromagnetic waves and is of the order of $2/3$ the speed of light in a vacuum, $2\times 10^8\,\rm m/s$.
The design of very high frequency equipment has to account for 'propagation delay'.

Finally there is the 'drift' velocity of the free electrons when they are subjected to an electric field which is of order $10\,\rm \mu m/s$ as illustrated in the answer to How to measure the speed of an electric current?.
Thus, superimposed on the random very high speed thermal motion of the free elections there is a average low speed movement of electrons along the wire in a particular direction which is what is called the electric current.
When you see animations of the movement of electrons the thermal motion is omitted as it would mask the very much slower drift speed of the electrons.

Consider it a simple model which one can be used to visualize what is happening on the molecular scale.

Farcher
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