What is actually moving in the wires? Electrons and energy, right? With alternating current, electrons move from atom to atom, practically back and forth in the wires. Mainly, it is energy that is being transferred from the turbine at the power plant through the wires. I have observed that on many electric meters, there is a wheel that turns. Energy turning the turbine, transferred over a long distance, turns that wheel on the meter.

I am seeking to describe the activity inside the wires in my home. I have read many books and web pages about this subject matter, however some information seems to be missing from the big picture. So I want to start at the circuit breaker box and ask about the activity going on in the copper. I am seeking a practical description of the movement of the electrons and the energy in the circuitry of my home.

  • $\begingroup$ Have a look at my answer to this question. It's not really a duplicate, but I suspect it will give you much of the information you need. $\endgroup$ – John Rennie Oct 2 '14 at 5:48

There is a simple picture that might help you: think of a wire as a pipe full of electrons. If you put pressure on one end of a pipe, the liquid in the pipe will transmit that pressure all the way to the other end. If you pump a little bit of liquid into a pipe, an equivalent amount of liquid will come out at the other end. It won't be the same liquid, though. The same thing is happening in wires. An electrical generator "pumps" electrons at one end into a wire. These electrons are pushing the electrons that are already in the wire towards the other end. At the load the displaced electrons begin to move and they can do some work, e.g. heat the filament of a lamp, move an electric motor or power an electronic circuit. If the power plant would put DC power on the wires, the electrons would be going all the way from the power plant to the load and back (on the ground wire), but that's not how we are doing it. It's much more practical to just pump a few electrons at a time into the circuit, and then "suck" them back. That's what an AC generator does. Electrons move one way, displacing other electrons, then they move backwards with each cycle. That's enough to transmit power.

I think for your purposes it's probably enough to stick with the pipe analogy, since it works just fine. Imagine a flow of electrons in pipes made of metal. Switches are disrupting this flow, so the electrons can't get from the power station to the load in your house.

Now... this is, of course, only the simplified version, and reality is not quite this simple. I will give you a hint of a better version now, which is much closer to the truth, but requires more abstract thinking.

As in the pipe example it's important to keep in mind that electrons are moving very slowly in wires. The energy is not actually transmitted by these electrons, but by an electromagnetic field that is in and around the wires. That electromagnetic field is moving at almost the speed of light (typically at two thirds the speed of light for most configurations of wires) and electrons can feel it, so if there is a strong electromagnetic field somewhere, electrons will feel a strong force acting on them.

So what the power plant does is to put an electromagnetic AC field on those wires and it's this field that moves the electrons locally. If you will, this is the microscopic explanation for the "pressure" in the pipe picture, but the details of that are so complicated, that you don't need to concern yourself with them.


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