I'm having a hard time conceptualizing what/how things are working in a voltage divider setup. I've read a couple other questions/explanations where the answerer has said to "not think about it in terms of water", but it's difficult to not do so, to some extent.
What I don't get is how the electricity changes/adapts after the FIRST resistor based on the ratio between it and the SECOND resistor? I know it's in the arena of having to do with "pressures" and pipes, but if you have a resistance further up in the chain of flow, conceptually how does it matter what the resistance is further down the pipe?
And stepping outside voltage dividers (but still in the realm of the question of voltage drop and ratios) — how/why does ALL the voltage get dropped over a resistor in a one-resistor circuit, but with 2+ resistors/loads, the electrons "know" to somehow ration the voltage drops proportionally? (Obviously I know the electrons aren't consciously working this out and making decisions). Why isn't a voltage drop static over a static resistance/load? Why does it depend on the other resistors/loads in the circuit?
(I don't mind technical, but if possible, please at least add some type of visual conception or demonstration, if you may! 🙂 Thanks!
Best Answer
Let's do another thought-experiment:
Imagine that we gradually shorten the connection between the two resistors until it is infinitesimally small. Now you effectively have one resistor with the divider-point somewhere in the middle. One end of this resistor is connected to the supply voltage, let's say 5 Volts. The other end is connected to ground, which we'll call 0 Volts because we'll use it as the reference point for our voltage measurement.
Again, imagine that we gradually move the divider-point up toward the 5V end or down toward the 0V end. At what location along this combined resistor would you expect the measured voltage to drop from 5 Volts to 0 Volts?
Is it clear that the voltage doesn't have a step change at one point, but is proportional to the fraction of the resistor below the divider-point? Voltage drop is linear along the length of the combined resistance.
Now imagine that we gradually restore the length of that connection we stretched in the first visualization. And imagine that the connection itself has no resistance - zero. (It's not quite zero, but it's so close that we can ignore it). Is it clear that the voltage will be no different at either end of the connection as you stretch it out again?
The total voltage drops linearly over the total resistance, and the divider point "samples" that voltage at a specific part of the total.
The current doesn't "care" or "know" whether is flowing through many individual resistors, or one continuous one; the voltage drops continuously along each segment of the resistance path. The "zero resistance" connections just don't matter.