Question: Does node analysis have any utility when designing a circuit step-by-step, or must the entirety of the circuit be known before node analysis is useful? Here's an example to illustrate what I mean.
Suppose that I have a 12V power supply, but I only want to have 6V across my lightbulb. So, when I go to design a circuit, I think through the steps I want the circuit to take:
- Reduce the 12V to 6V.
- Send those 6V across the lightbulb.
To tackle step 1, I decide that I will use a voltage divider. Thus, I build the following circuit:
If I perform a node analysis on this voltage divider alone, then I will find that I do indeed have the 6V that I was seeking at my output node. However, when I move on to step 2, I'll find that my circuit will not work because I neglected the fact my lightbulb has some resistance. (We'll say 100 ohms.)
Now, when I add my lightbulb, there will only be 4 volts across it. Thus, it seems that my previous node analysis was unfruitful because I had yet to determine all of the components of my circuit.
Yet, it seems that, in most literature, node analysis is performed on "incomplete" circuits. Does this imply that node analysis can still be useful before a full circuit is determined? Or is it just a shortcut taken to avoid wasting time with extraneous information?