How are voltage dividers used in circuits?
Voltage dividers are usually used to reduce the voltage to provide a fraction of the supply voltage to a device - a transistor's base, for example. For LEDs we control the current with a simple series resistor. While it does reduce the voltage we don't refer to it as a voltage divider due to the non-linear ratio caused by the diode's characteristics.


  The main issue that concerns me is where the drop occurs. Before the resistor or after the resistor.


Voltage is dropped across both the resistor and the LED. This can be confirmed with a simple experiment.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. (a) Resistor then LED. (b) LED then resistor.

I've chosen the resistor as 1k to provide about 10 mA which will light most small LEDs brightly.


VM1 will measure about 10 V.
VM2 will measure about 2 V due to the forward voltage, VF, of the LED.


You can swap the LED and resistor as in Figure 1b and the end result will be the same. Note that neither component is "aware" of the other's position.



Figure 2. LED IV curves showing the non-linear relationship between current and voltage in various colours of LED. Note that the VF is dependent on the doping of the semiconductor and the doping determines the colour. Image source.