The discovery and application of electricity was an important milestone in the development of human civilization, and today, electricity has been deeply integrated into all aspects of our daily life and has become an indispensable part.
As far as we know, the current is formed by the movement of electrons, so it seems that when a generator supplies power to electrical equipment, it should be sending electrons to electrical equipment continuously, but we have never seen a generator run out of electrons, which is a bit puzzling, why can't the generator run out of electrons?
To figure this out, let's take a look at a very simple circuit diagram (shown below).
The physics teacher told us that the free electrons in the conductor will only form an electric current when they move in a regular direction, so how to make the electrons in this circuit move in a regular directional motion? The answer, of course, is to close the switches in this circuit. In fact, this is actually a necessary condition for the formation of an electric current – a closed path.
If we consider the power supply in this circuit diagram as a generator, we can conclude that the electrons in the circuit are not actually consumed during the normal power supply of the generator, but are in a state of "recycling".
We can simply understand that electrons are constantly "departing" from the negative pole of the generator, while at the same time, the electrons in the circuit are constantly "returning" to the positive pole of the generator.
You may ask, isn't the direction of the current from positive to negative? Why is it said that electrons "depart" from the negative electrode of the generator?
This is actually because when people first proposed the concept of electric current, they did not know the existence of electrons, but only defined the direction of electric current according to the phenomena observed experimentally at that time, although it was later discovered that the direction of movement of electrons was opposite to the previously defined direction of electric current, but because this concept has been used for too long, it has not been changed.
It should be pointed out that in the process of the generator supplying power to the electrical equipment, in fact, it is not the electrons that "start" from the negative pole of the generator to do directional motion alone, in fact, in this process, the role of the generator in the circuit is actually to provide electromotive force for the entire circuit, and then exert an electric field force on all the electrons that can participate in the conduction, and drive them to start directional motion almost at the same time.
(As you can see in the diagram above, the circuit is actually full of free electrons, and the moment we close the switch, all the free electrons in the circuit will start to orient almost at the same time.)
Why do you say "almost at the same time"? This is because the speed at which an electric field builds up and propagates is finite, but this "finite speed" is very fast, about 300,000 kilometers per second.
Doesn't it sound familiar? Yes, this speed is actually the speed of light, and because of this, we usually say that the speed of electricity travels is the speed of light.
However, it should be noted that the propagation speed of electricity is not the speed of the directional motion of electrons, in fact, when forming an electric current, the directional motion speed of free electrons in the circuit under the action of electric field force is actually very slow, how slow is it?
Let's put it this way, in an ideal world, when a current of 1 ampere is passed through a standard copper wire with a diameter of 1 millimeter, the directional velocity of free electrons within the wire is only about 0.1 millimeters per second, which can be said to be ridiculously low.
To sum up, in the process of generator supplying normal power to electrical equipment, although the current is formed by the movement of electrons, the electrons themselves are not "consumables", and when the current is formed, they will always be in a state of "cyclic use" in the circuit.
We can simply understand it as: for the generator, its negative pole will continue to send electrons, and at the same time, its positive electrode will continuously "recycle" the electrons in the circuit, in this case, of course, the generator will never run out of electrons.
You may be asking again, the principle described above is only based on direct current, but what about alternating current?
In fact, the reason is almost the same, simply put, alternating current is actually the current direction of the current periodically changes with time, and to form such a current, it also needs a closed path, the difference is that in this closed path, the directional direction of the free electrons is forward for a while, and backward for a while, but on the whole, these electrons are still in a state of "recycling" and will not be consumed.
So, if electrons are not consumed, then what is consumed when we usually use electricity?
To put it simply, what we consume is actually the energy carried by the directional movement of electrons, which will be converted into various forms of energy (such as mechanical energy, light energy, thermal energy, etc.) through various effects (such as electromagnetic effect, thermal effect, chemical effect, etc.), and then drive the normal operation of electrical equipment.