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I understand that when connecting an LED and a resistor in series; the resistor can be placed on any side of the LED as the current will remain same in a series connection. Please correct me if I'm wrong, but I was under the impression that conventionally the electrons flow from positive to negative. So shouldn't the resistor be placed before an LED to limit the flow of charge.

In this scenario the negative is connected ground and the positive to a power source. So I don't understand the chain Link analogy as well. Where the whole chain moves as a whole because here the flow ends with the GND right ?

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Another way to look at it is this:
Imagine the current flowing through the LED toward the resistor to be greater than the current flowing out of the resistor toward ground. The only way this could happen is if some of the charge - the difference due to the different currents - accumulated in the resistor. But that cannot happen forever, and not even for any appreciable length of time. (If it could, and did, the device would eventually fail - spectacularly!) So, because charge in must equal charge out over time (and over a very short period, at that) current in has to equal current out.

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  • Charge per unit time.
    – Ignacio Vazquez-Abrams
    Commented Oct 30, 2014 at 17:28
  • Wow. That cleared things up. Thank you !! ... So resistance is basically the action of electrons moving slower as the electromagnetic force in the insulator is higher rite ?
    – Hemanth Reddy
    Commented Oct 31, 2014 at 6:32
  • Slower in the flow sense or electrons per unit time. And as I understand resistivity, it doesn't involve electromagnetic force but the availability of free electrons. More free electrons available to move through the material -> lower resistivity (and I'm somewhat beyond my knowledge here, but here is a section of a Wikipedia article that discusses it briefly).
    – JRobert
    Commented Oct 31, 2014 at 15:28
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Resistor on any side of led will intercept current flow. Just use another analogy with water, tube and water tap.

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