Monday, 30 March 2015

Why do LEDs not obey Ohm's law?


In a previous question, it was brought to me that LEDs do not obey the Ohm's law. (See Calculate expected voltage around a resistor)


Simply put: how is that?


What makes them behave so differently? How should we treat them in a circuit and calculations?


Are there other components with similar behavior?



Answer



Ohm's law applies to resistance. All resistive aspects of a device will behave according to OHm's law.


If you invert your question you see that every thing that behaves according to Ohm's law must be a resistor. There is only so much that one can do with pure resistance. So logically the anything that doesn't behave according to ohms law isn't a resistor. Or any thing that isn't a resistor won't behave according to ohms law.



I believe that is called a Tautology.


In circuit design we have many different devices all having unique properties to be able to implement different things/functions.


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