Electronic – Voltage drop across a single resistor and across two resistors


I have been having difficulty understanding voltage drops across resistors. Now, I know the theory and how to apply Ohm's law.

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The question is why does the voltage drop across resistors of the same resistance vary from the first circuit to the second circuit? Does it have anything to do with current? Why does it happen? I am trying to find an intuitive explanation as to why it happens.


Best Answer

Your 2 × 100 Ω resistors are in series so your total circuit resistance is 200 Ω and this will restrict the current to half of the value obtained in the single resistor circuit.


simulate this circuit – Schematic created using CircuitLab

Figure 1. An equivalent circuit using a potentiometer.

Here we've replaced the 2 × 100 Ω resistors with a 200 Ω potentiometer with its wiper in mid position. It should be clear that:

  • When the wiper is at the bottom of the resistance track the output will be 0 V.
  • when the wiper is at the top of the track the output will be 16 V.
  • When the wiper is anywhere in between the output voltage will be proportional to the fractional distance from the bottom to the top.

In your example you have equal resistances so the voltage will be 8 V.

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