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I am basically a software engineer but have some interest in electronics so this is probably a very basic question.
I understand theoretically a battery or power source can provide as much current as needed by the circuit. However, I see in battery charger they say 5v and 500 mA. I don't understand what this is. Isn't it the current will be drawn as needed by the circuit? I understand if too much current is drawn it might burn something.... but having a current specified on charger (or a power source) is what I don't understand. Same is the thing in case of computer's USB (I heard it cannot supply more than 500mA. what if a circuit tries to draw more than 500mA?).
Hope I was able to explain my question well.