Some really basic conceptual points I'm currently confused on:
- My physics textbooks tell me that the term "voltage" or "potential difference" only makes sense in reference to a pair of points in a circuit. Yet it seems like electronic engineers are constantly talking about the voltage at a single point. For example, from the wikipedia page on op amps:
So what do they actually mean? What is the implicit second point in each case?V+ is the voltage at the non-inverting terminal, V- is the voltage at the inverting terminal, and AOL is the open-loop gain of the amplifier. - This tutorial about LEDs on ladyada.net was extremely helpful, but I want to make sure I really understand why the method of calculating the current through the LED makes sense. The tutorial seems to imply (but without quite saying it) that the voltage drop across the LED is constant (equal to its "forward voltage") at any current -- does this mean that LEDs, or diodes in general, are made of some magical substance whose resistance varies as necessary in order to keep a constant voltage across the leads? That's the only way I can reconcile what the tutorial says with Ohm's law.