Energy doesn't FLOW the way you THINK! (Electrodynamics)

How does AC really work if the charges don't go anywhere? The answer to this threw all my intuition out the window. Get ready. This episode was made possible thanks to the generous support of Patreon supporters. Hello weirdos. You should not confuse charge movement with

energy

movement. They are not the same. Let's define both carefully. Electrical current, or "current," is the

flow

of positive charge. Wait, what is positive charge? Yes, you can thank Ben Franklin for that. To the timeline!! In 1748, Ben Franklin made two statements about electricity. One: amber turns negative when you rub it. Two, current is a

flow

of positive charge. 150 years later JJ Thomson discovered the electron and we saw that we had a problem.

We would be expected to adapt Franklin's definitions, but no. We went even further. Even knowing that the negative charge moves with the current, we act as if the positive charge moves in the other direction. The stubbornness of people never ceases to amaze me. We have to live with it now. Electric current is the flow of positive charge and we measure it in amperes. The flow of

energy

can best be described as power. In other words: the rate at which energy is used and is measured in joules per second or watts. Shut down for watt reasons? Current and power are related.

Current is the charge over time and voltage is the energy per charge, power is the current multiplied by the voltage. It's a pretty simple calculation. But the original question was not about quantities. But about the direction. This comparison says nothing about the direction. Isn't it energy carried by charged particles? Don't current and power go in the same direction? Yes to the first question and no to the second. Charged particles have energy, because everything has energy, but that energy does not power the devices. For convenience, we take a light bulb. What I'm going to explain applies to everything, but we don't want to get bogged down in details.

So let's leave the light with a simple battery. The positive side has a higher energy than the negative, so if you give the charges a path, they will go to the lower energy. That's what electric current is. Over time, battery power decreases when devices are used. It can cause a lot of panic if it is our mobile phone, but the same goes for our light bulb. Battery power decreases when heat and light are irradiated. The energy flow is described by the Poynting vector. No, that's not a typo. The name comes from John Henry Poynting, the guy who came up with it.

It's a play on words, the dot indicates the direction of flow. I like word games. Here is the Poynting vector. E is the electric field, B is the magnetic field, and mu is just a constant to make everything work. Don't worry about that. This gives us the energy per second that flows through a surface. A common example is light. Light is an electromagnetic wave, a disturbance in electric and magnetic fields that creates a flow of energy. This is what it looks like in a light bulb. But the Poynting vector is for all electric and magnetic fields, not just those found in light.

What's up with those fields again? Hmm, I can handle it quickly. The charge affects the electric field and the moving charge affects the magnetic field. These fields are not connected to the load. They sit in a fixed place while the load moves. Without cargo nearby, the fields are still there. They are simply zero. The same goes for batteries. You can

think

of this battery as two equal but opposite charges. These charges influence the electric field. But according to the Poynting vector, we cannot get an energy flow without having a magnetic field. The battery

doesn

't simply lose energy.

It must be connected to something. Here is the electric field, drawn simply. If we connect some cables and a lamp, the field is somewhat disturbed. Although the load on that extra material is balanced, the field is guided by it. The field in those materials is strong enough to drive the charge. Now that the circuit is closed, the electric field becomes a stable current and with a moving charge a magnetic field arises. Now we have an electric field and a magnetic field. According to the Poynting vector, we obtain an energy flow. But this cross product means that the current is perpendicular to both fields.

The charge flows in the same direction as the electric field, which cannot be the same as the energy flow. According to Poynting, energy does not flow in the same direction as the load. Hope for?! Precisely! When I realized this, I lost my intuition about the circuits, but this is what it looked like when I put everything back together. If we get close to one of the wires, we have a strong electric field inside that drives the current and a small electric field on the outside. We also have a magnetic field inside and out. With the Poyting vector we achieve an energy flow towards the center of the cable.

The energy comes from the field outside the wire! Guard! Didn't you say the power came from the battery? Yes, but it happens indirectly. Inside the battery, the electric field points in the opposite direction, but the magnetic field points in the same direction. If we look at the battery in the same way, we see energy flowing from the battery to the field. So the energy that the wire and lamp get from the field is the same amount that the battery loses to the field. The energy flow in the circuit looks like this. It's crazy! Regardless of whether it is alternating or direct voltage.

With alternating current, the current simply flows back and forth because the electric field keeps changing direction, just like the magnetic field. When this and that change direction, they cancel each other out. The flow of energy maintains its direction. Even with alternating current, the power flow leaves the source and reaches the devices. How is that possible? Aren't the generators miles away? Yes, but that

doesn

't matter. After all, these fields are everywhere and are affected by load everywhere. The power coming from a source does not have to be the same as what goes into your device. Conservation of energy simply says that the numbers are the same.

If you calculate the energy flowing through the cable, you get exactly what we lost in heat and light. How does energy flow through the circuit? The energy comes from the fields surrounding the circuit. A source, such as a battery, supplements what has been used and the circuit is the mechanism to keep the energy flowing. And are you as baffled as I am? Share it in the comments. Thanks for liking and sharing. Don't forget to subscribe if you want to stay up to date. And remember, it's okay to be a little crazy. The featured comment is 'space is where we belong!' Who asks: Is the wind just a push to make the tap turn?

No, no, we do not make perpetual motion machines. The current generated resists the movement of the coil. Without continuous wind pressure, the coil stops almost immediately. Thanks for watching.