Recently when I was procrastinating, I have learned that an electric energy is not propagated via wires but through fields. Once a circuit is closed, a field is created and it carries the energy from a source to eg a light bulb. It proposed a question to me.
The question is, how does the current/source know that the circuit has been closed?
Let’s ask two similar questions, both assume ideal conditions.
1. we have a source and a switch on Earth and a light bulb on Mars. We close the circuit using the switch and the energy starts to be emitted from the source in an almost instant. After some time, once the field reaches the bulb, it starts to emit light.
2. we have the same situation, but the switch is moved to Mars. Will it take the same time for the bulb to emit light? How does the source know that the circuit has been closed and it can start to emit and electric field?
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Current flows from high potential to low potential. It’s sort of like how if you hold a ball over your head, and let go, it will fall to the ground. How does the ball know that it’s higher than the ground? It doesn’t… it’s just constantly attracted to the ground, and once you remove the thing that’s keeping it from going to the ground, it’ll fall.
In the case of a circuit, when you flick the switch, you connect an area of high potential (the power supply) to an area of low potential. Again, the high potential current always wants to flow, and when you give it a way to flow, it’ll flow.
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