Hi all!

I have an indirect power source that’s powering a DC motor, and I’m attempting to measure the power generated by the motor.

I have the motor connected in circuit with a 10 Ohm resistor to the analog pin on the Arduino, and I’m taking the analog input and multiplying it by 5 volts / 1023 units to get the voltage. Would I then just take that value and square it, then divide by 10? (P = V^{2} / R)

When I do this, I get a power of about 0.04 Watts. However, according to the performance curves of this motor, at the RPM it’s operating at, it should be generating about 3 Watts.

Where am I going wrong? Either the analog pin reading is too low, or my formulas are incorrect. Any help would be greatly appreciated, so thanks in advance for your time.