- #1
YoshiMoshi
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Homework Statement
Ok so I remember learning KCL. Current is either entering or leaving the node. There's only two possible option. You can call entering the node positive or negative, you can call current exiting the node either positive or negative. As long as what you call entering the node not the same thing as what you call leaving the node.
Ok great. I never questioned that. But I want to know the real reason why. Yes I know this is "just how it is", "convention"...
There's only two options agreed. So it's like I either put money into the bank account or It take it out, or let it stay in there so maybe this is a bad analogy.
But I guess if it's either going in or out, but has multiple pathways to go in or out, than why do we associate with only two possible scenarios positive or negative?
Example, there's a four way intersection. There's a car "moving forward" into the intersection. I define a coordinate system at the center of the car so that the "moving forward" direction is positive X, moving in the opposite direction is negative X. The car enters the four way intersection and turns left, during this whole process the car continues to move forward. Meaning as it rotates to make the turn, the coordinate system rotates with it meaning it never went in "reverse". So we associate such movement as going in only one direction "forward" and not "reverse" at all.
Even if I defined a coordinate system at the middle of the intersection (node) than I have four possible directions from the origin to travel, or if it was grass field many at different angles with respect to a two axis system.
So what gives with current entering and leaving a node? Does it have to do with something along the lines of the charge entering the node, isn't necessarily the charge that went down path A to component Z, it could have gone down path B to component Y? Ok but as long as the current doesn't start going in the reverse direction back from were it came and the charge never goes in the reverse direction than why is it associated with the opposite direction.
Homework Equations
The Attempt at a Solution
I know by convention and so forth. Ok fine, but when I think of an analogy of car entering an intersection the relationship doesn't seem to hold. I never questions KCL while learning circuits. Just sort of the old this is the law don't question it it's correct. Learn all about circuits without knowing why it's the law or the truth.