For example sometimes people will ask whether it matters what side of a component you place a resistor on. Surprisingly, it doesn't matter because electrons behave as if they're all connected together on a conveyor belt — if they encounter resistance in one spot they slow down everywhere else. It's not as though it's very fast on one side and then slower on the other.
Why is this the case? How do the electrons "know" to slow down even well before they actually encounter a resistor that may be on the other side of a component?
Best Answer
They actually don't. Know, that is.
There are tree parts of this answer. First, they might never encounter a resistor on the other side of a component. Considering that speed of electron in a copper is somewhere in micron/s range chances are your particular electron will never even reach that resistor before you turn your circuit off.
Second, what you describing as "conveyor belt" is actually a flow of energy, not the movement of electrons. And energy transfer is happening close to the speed of light, which is fast but not instantaneous. Consequently, any changes or disruptions in a circuit do not happen immediately, it just looks like that because of high speed of wave propagation.
And finally, if you put one and two together, the resistor placed in a circuit does not "slow down electrons on a conveyor". What it does is make energy transfer harder, so the total energy flow in the circuit is reduced.
The analogy with water in pipes while being useful is technically incorrect, because the speed of water flow depends on pipe diameter according to Bernoulli's principle. Furthermore, the amount of electrons in a conductor is enormous. If you really want to compare electricity to water you should use at least a river.
Now, the river does not have to flow fast to pass wast amounts of energy. Imagine the force of water pushing down on water wheel lowered into the river. The bigger the wheel, the more power is generated. With big enough wheel even slow river can produce huge force.
So, what happens if you somehow manage to block a river upstream? The speed of flow will be pretty much the same, but the level would drop, and so would the pressure on our hypothetical huge water wheel. That is how resistor in a circuit works. Also important to note, that there will be some delay between blocking upstream and reducing the power downstream, just like it happens with electricity, only on different time scale.