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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It is not a matter of the source “knowing” it is just a matter of the source doing what is either natural or it is designed to do.
If you are not interested in electricity then you can think of any source with potential energy as analogous to an electric source. If you put a hole in a balloon, you know air will come out. If you drop a rock, you know it will fall. If you close a switch, you have created a path for electricity to flow.
Electricity flows at the speed of light, so in your earth-mars question, there will be a measurable delay based on the distance of each example
Electricity can be as intuitive to understand as a rock fall because of gravity if you understand the basics principles of electrons
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