How do passive circuits work with no battery/power source?
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Well it has to be a component that uses Faraday’s law to drive the circuit.
Many examples in everyday life al the way from RFID energy harvesting to galvanic isolation. Both use the same principle. Even transformers.
It doesn’t even have to be Faraday’s law. A photo diode is another example. But this is the only example I can think of that doesn’t use Faraday’s law. Even hand cranked devices is an example of faradays law.
I guess the answer is Faraday’s law. You may find only exceptions like a photo diode or say a solar panel.
Even power plants use the same principle as a store bought hand-cranked torchlight.
Edit: I just saw the other comments, idk why so many people are providing definitions and examples of what a passive and active circuits are. That’s not what the post is asking.
It’s very simple. A passive circuit cannot work without a power source. That’s in the definition.
By extention, you have two components in impedance and power: real and reactive. The reactive component is the imaginary part that capacitors and inductors produce. The real, unreactive components are resistors. Technically everything produces heat losses and has some resistance.
The real part is the part that produces heat losses. The reactive or imaginary, part produces losses by way of phase changes and depending on the application, bouncing back energy. Imaginary power is a very intriguing concept.
To get an accurate idea always convert everything into polar form.
I mentioned this because not all passive components theoretically produce heat losses, but practically do. But again, depending on the application, heat losses aren’t the only type of losses.
Edit: at the end of the day, a passive component does some work, that it’s designed to do.
Something to keep in mind is engineering is very purpose driven.
Edit:
Maybe you can think of passive circuits as ones “waiting” to receive power.
When you cover Thevenin’s theorm or start Signals and systems it should become clearer.
When you cover thevenin’s theory, you’ll learn to look at a circuit as a black box.
When you cover Signals and Systems, you’ll learn to look at a circuit as a Transfer Function. In a way, a mathematical extension of the same concept.
Edit: some of these comments are scary. Hope they’re not practicing engineers. Holy fuck its scary.
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