Using a resistor to drop voltage for LED
By putting the resistor in series with the multimeter leads, you will always see a voltage of 5V since the multimeter (with effectively infinite resistance) will act as a potential divider with the source, and compared to the 91 ohms, your meter will take up all of the voltage. This happens no matter which way you connect the meter. Whats worse is that the LED isn't even connected to begin with. The voltage dropping happens when the circuit is fully connected, and for a voltage to actually drop, a current has to flow. Connect your circuit so that it turns on, then connect your voltmeter in parallel to each source. You will observe that the voltage across the LED is 3.2V, and across the resistor is the remaining 1.8V (This is due to KVL but i wont get into that).







simulate this circuit &ndash; Schematic created using CircuitLab