Potentiometers, also knows as pots, are useful electrical components that allows a person or a machine to directly tune the voltage or restiance in one part of a circuit. In its normal configuration, a potentiometer acts as a variable voltage divider. If a voltage source is connected between the two pins called terminals, the voltage over the third pin, known as the wiper will vary with the position of the potentiometer shaft. This shaft can for example be controlled by a slider or a thumbwheel.

Model

In this example model, a thumbwheel potentiometer has been connected in a rheostat configuration, working as a variable resistor. The terminal pin connected to the ground has been short-circuited with the wiper pin. This means that the voltage over the terminal to the wiper will be the same as over the two terminals. The rheostat has been connected in a series with a motor. The motor in turn drives a body with inertia.

The torque produced by the motor will be proportional to the current running through the motor. Since the motor is connected in a series with the potentiometer, the current throught the motor will be the same as the current through the potentiometer. By turning the potentiometer the motor torque can be controlled.

Simulation

To simulate the model, click the Simulate button:

Plot the results

Explore how the torque from the motor increases as the thumbwheel is turned. Plot the Model plot called Motor torque by double clicking it from the Model Plots section.

You should now see the graph below: