Electrical – Lowering resistance of potentiometer

I saw a video where a person wired a resistor to the outer pins of a potentiometer to lower the resistance. Does this work?

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. (a) R1 has no effect on the potentiometer. (b) R5 does have an effect on the potentiometer.

• In Figure 1a the potentiometer is driven by the preceding amplifier which will use negative feedback (not shown) to drive the output to the desired level. Adding R2 makes no difference in this case other than to waste power.
• In Figure 1b R4 and R3 form their own potential divider which limits the voltage when R3 is at the "max" position. The max value will depend on the ratio of R4 to R3. By adding R5 in parallel with the potentiometer we cause a greater voltage drop across R4 and this again decreases the maximum output of the potentiometer.

The overall effect will also depend on what impedance is connected to OUT.

You can model this in a spreadsheet using the series and parallel resistance formulas. Alternatively set it up in a simulator such as CircuitLab (available on the editor toolbar on this site) and do a sweep simulation. In Figure 2 I've run a DC sweep on R2.K (the wiper position) and obtained the result of Figure 3.

^{simulate this circuit}

Figure 2. Circuit for simulation.

Figure 3. Results of simulation.

Note the non-linearity as a result of the relatively high load of R4.