How exactly does an electrical circuit carry energy?
I understand that particles (protons and electrons) have “charge”, and opposite charges attract. And that electrons supposedly migrate very slowly along wires, and as they do so this creates an “electromagnetic field”.
What exactly is this electromagnetic field? What does that mean?
And if the electrons are not carrying the energy, how does it work? How does a circuit make a lightbulb glow at the atomic level?
In: Physics
Similar to water in a river, water itself does not carry energy, it’s the movement of water that carries the energy.
Water pushes stuff around and we use that to power things like water turbines. We also use moving magnets to push electrons through the wire and so the EM field of those electrons also move.
Electrons and EM fields push stuff in the appliances to make them move, that’s how the energy is transferred and utilized.
I’m going to address these out of order because the middle question is actually the hardest to answer.
>electrons supposedly migrate very slowly along wires
Electrons are slow, the wave is not. Passing current through a wire is kind of like pushing water through a hose. But the hose is not empty. The water is not starting at one end and moving all the way to the other. It’s more like pushing water into a hose that is already full of water. The water goes in one end, and the resulting wave of molecules bumping into each other makes the water at the other end come out almost instantaneously.
>And if the electrons are not carrying the energy, how does it work?
The electrons are not carrying the energy. Their movement IS the energy. The electrons jump from atom to atom until they encounter an obstacle they can’t get through. This is resistance. The charge differential is still pushing and pulling the electrons but the material impedes their movement. So they go apeshit and bounce around in all different directions. The resistant material gets hotter and begins to glow because so many electrons are being bounced around. The more the current has to struggle to get through the material, the more electrons are wasted, the more the material heats up.
>What exactly is this electromagnetic field?
An electromagnetic field is a physical field that occurs between electrically charged particles. Electromagnetic waves are emitted by electrically charged particles undergoing acceleration, and these waves can subsequently interact with other charged particles, exerting force on them. When one charged particle gets nudged by the electromagnetic force, the movement propagates to the next one, and the next one, and the next one. It’s kind of like a ripple travelling through water.
Okay, but what actually IS the electromagnetic force? What’s the thing making the charged particles move in the first place?
We don’t know.
Electromagnetic force is one of the four “fundamental forces.” Once you get to a fundamental force, you have reached bedrock. There’s nothing below it. We can measure the effect of the force, and we can observe the movement of particles resulting from the force, but we can’t explain how and why it happens.
A battery pushes electrons at one end of a circuit and pulls them at the other end. This gives direct current. A wall outlet goes back and forth between pushing and pulling, which gives alternating current.
Electrons hate each other and push away from each other. They love protons and pull toward them if they can. So whichever way the electrons are getting shoved, each one shoves on the next. They don’t move very much, but a wave of annoyance goes down the wire at nearly the speed of light. That wave is electric current.
In a lightbulb, there are electrons holding onto the protons in the filament in the bulb. If those electrons move, it also gets the protons moving, and the amount that they’re moving is heat.
As the filament heats up, it makes the electrons excited with energy, which pushes them away from their beloved protons. They get back toward the proton by releasing that energy as light.
So an incandescent lightbulb works equally well with direct and alternating current, because all that matters is how much the electrons are jostling around, not which way they’re going at any given moment.
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