Thanks again Paul. I am wondering if you have a view on what seems to have been a bit of a debate [here seen in YouTube] about whether electrons actually do “flow” in wires… https://youtu.be/bHIhgxav9LY
Thanks for the questions! The core insight of the analogy is that the energy that powers electronics is electrical potential energy from the position of electrons in an electric field, and the energy that powers water wheels is gravitational potential energy from the position of water in a gravitational field. I find this an extremely useful connection that explains how electricity can be so useful, which is why I wrote this article.
Electrons do flow in an electric circuit. Without a power source, the electrons in the wire are moving extremely fast but in completely random directions. It is impossible to harness energy from this random motion because everything cancels out. When a power source is used to produce an electric field, the electron's motion remains almost random, but now with a slight tendency to be more likely to move towards the positive terminal than in the opposite direction. This tendency is what makes it possible to harness energy from their motion. (This is shown well in the follow-up to the video Bill linked at 2:50 - https://youtu.be/oI_X2cMHNe0?t=170). The same effect is happening in a river. Even in still water, the water molecules are actually moving extremely quickly but completely randomly. If the body of water is inclined, then molecules become slightly more likely to move in the direction of the incline which we observe as a flow and which provides energy we can harness with a water wheel. So electrons in a wire flow in the same way as water molecules in a river.
However, it is true that it is a simplification to say that electricity is transmitted from power plants to our devices by the flow of electrons. There are a number of additional complexities, as identified in the video. But some of these can also be added into the water analogy. For example:
1) Mains electricity is an alternating current, so electrons do not flow in one direction around the circuit but oscillate back and forth. This is like a canal with a water wheel in the middle that is periodically tipped to reverse its incline, so that water initially flows from left to right and then later flows back from right to left. The water flowing in both directions can be harnessed to turn a water wheel, just like an alternating electric current provides electricity as it flows in both directions.
2) The connection of wires from power plants to our home and within our devices includes transformers. Transformers have two wires separated by a gap; electricity does not cross the gap but instead the current flowing in one wire is used to generate a current in the other wire, transferring energy from the first wire to the second in the process. This is like water in one canal turning a water wheel that powers a pump to lift up water in a separate canal in order to allow it to flow.
One aspect that I think is different about electricity is the role of electromagnetic waves. The thought experiment at the beginning of the video Bill linked (which is revisited in more detail in https://youtu.be/oI_X2cMHNe0) depends on the fact that enough energy is transmitted by electromagnetic waves directly from the battery to the light bulb to illuminate it. These waves induce an electron flow in the light bulb that can illuminate it temporarily even if electrons are not flowing through the whole circuit. We can create waves in water that similarly provide a fast-moving pulse of energy by disturbing the water, but this is not really analogous since the energy is not then provided by gravitational force on the water. Technically, the analogue is gravitational waves in the river. These waves are produced - and are truly analogous to electromagnetic waves - but they are so incredibly weak that they are completely undetectable. This is because gravity is so much weaker than electromagnetism as a force. The result of this is that effects can be produced with electricity using electromagnetic waves - like that in the thought experiment - that cannot be produced with gravity acting on water.
In summary, electrons do flow in a wire. However, they are not generally transported all the way around the circuit and this is not necessary to provide energy through their flow. The energy provided by electrical circuits is the electrical potential energy from the position of electrons in an electric field. This energy can be said to be contained in the electrons, or in the field, but in reality it depends on both. The energy can be understood to be carried by electromagnetic waves, but the transfer of a substantial amount of energy by these waves ultimately depends on the flow of electrons in the wire. I don't think that any of these facts are open to debate; I think that it is simply a question of which perspectives on the phenomena are most helpful for understanding and communication. The approach I took in the post is what I find most helpful, so I hope it was helpful to you and the other readers as well!
Thanks again Paul. I am wondering if you have a view on what seems to have been a bit of a debate [here seen in YouTube] about whether electrons actually do “flow” in wires… https://youtu.be/bHIhgxav9LY
I was about to ask the same question. Is there actual transport of electrons? How far does the water metaphor go?
Thanks for the questions! The core insight of the analogy is that the energy that powers electronics is electrical potential energy from the position of electrons in an electric field, and the energy that powers water wheels is gravitational potential energy from the position of water in a gravitational field. I find this an extremely useful connection that explains how electricity can be so useful, which is why I wrote this article.
Electrons do flow in an electric circuit. Without a power source, the electrons in the wire are moving extremely fast but in completely random directions. It is impossible to harness energy from this random motion because everything cancels out. When a power source is used to produce an electric field, the electron's motion remains almost random, but now with a slight tendency to be more likely to move towards the positive terminal than in the opposite direction. This tendency is what makes it possible to harness energy from their motion. (This is shown well in the follow-up to the video Bill linked at 2:50 - https://youtu.be/oI_X2cMHNe0?t=170). The same effect is happening in a river. Even in still water, the water molecules are actually moving extremely quickly but completely randomly. If the body of water is inclined, then molecules become slightly more likely to move in the direction of the incline which we observe as a flow and which provides energy we can harness with a water wheel. So electrons in a wire flow in the same way as water molecules in a river.
However, it is true that it is a simplification to say that electricity is transmitted from power plants to our devices by the flow of electrons. There are a number of additional complexities, as identified in the video. But some of these can also be added into the water analogy. For example:
1) Mains electricity is an alternating current, so electrons do not flow in one direction around the circuit but oscillate back and forth. This is like a canal with a water wheel in the middle that is periodically tipped to reverse its incline, so that water initially flows from left to right and then later flows back from right to left. The water flowing in both directions can be harnessed to turn a water wheel, just like an alternating electric current provides electricity as it flows in both directions.
2) The connection of wires from power plants to our home and within our devices includes transformers. Transformers have two wires separated by a gap; electricity does not cross the gap but instead the current flowing in one wire is used to generate a current in the other wire, transferring energy from the first wire to the second in the process. This is like water in one canal turning a water wheel that powers a pump to lift up water in a separate canal in order to allow it to flow.
One aspect that I think is different about electricity is the role of electromagnetic waves. The thought experiment at the beginning of the video Bill linked (which is revisited in more detail in https://youtu.be/oI_X2cMHNe0) depends on the fact that enough energy is transmitted by electromagnetic waves directly from the battery to the light bulb to illuminate it. These waves induce an electron flow in the light bulb that can illuminate it temporarily even if electrons are not flowing through the whole circuit. We can create waves in water that similarly provide a fast-moving pulse of energy by disturbing the water, but this is not really analogous since the energy is not then provided by gravitational force on the water. Technically, the analogue is gravitational waves in the river. These waves are produced - and are truly analogous to electromagnetic waves - but they are so incredibly weak that they are completely undetectable. This is because gravity is so much weaker than electromagnetism as a force. The result of this is that effects can be produced with electricity using electromagnetic waves - like that in the thought experiment - that cannot be produced with gravity acting on water.
In summary, electrons do flow in a wire. However, they are not generally transported all the way around the circuit and this is not necessary to provide energy through their flow. The energy provided by electrical circuits is the electrical potential energy from the position of electrons in an electric field. This energy can be said to be contained in the electrons, or in the field, but in reality it depends on both. The energy can be understood to be carried by electromagnetic waves, but the transfer of a substantial amount of energy by these waves ultimately depends on the flow of electrons in the wire. I don't think that any of these facts are open to debate; I think that it is simply a question of which perspectives on the phenomena are most helpful for understanding and communication. The approach I took in the post is what I find most helpful, so I hope it was helpful to you and the other readers as well!