# Sharing the Load: Power Ratings

I have some cheap potentiometers that I would like to use as variable resistors.

The potentiometers have a power rating lower than the amount of power I would like to be able to dissipate across the setup at a fixed voltage, so I have a plan.

Instead of using a single potentiometer set to resistance X and total voltage drop of V, I will put the two variable resistors in series and set both of them to a resistance 1/2 X. The voltage drop across each will now be 1/2 V.

Because the total current will stay the same thanks to an equal equivalent resistance, each variable resistors will get the same current as the original setup with only one variable resistor.

Because P = IV, each resistor should dissipate half the power with half the voltage drop. The total power will be the same, but because I have two potentiometers in series, given that I adjust them to the same resistance each time, I will be able to dissipate twice the total power ago a given total resistance.

Is there a flaw in my reasoning?

The maximum current it can handle is (from $$\ P = I^2R \$$) given by $$\ I = \sqrt{\frac {P}{R}} = \sqrt{\frac {0.125}{250}} = 22\ \text{mA} \$$.
At, say, a 40% setting the maximum power allowed would be $$\ 0.125 \times 0.4 = 0.05 \ \text W \$$.