What is the function of a potentiometer in a circuit?

A potentiometer functions primarily to adjust the voltage in a circuit. It consists of a resistive element and a sliding contact, which allows the user to tap off a portion of the voltage across the resistive element. By turning the knob or adjusting the slider, the user can change the resistance and consequently the voltage across the load connected to the potentiometer. This ability to vary voltage makes it a valuable tool in various applications, such as controlling volume in audio devices, adjusting brightness in lighting, and varying speed in motors.

The other choices do not accurately describe the primary role of a potentiometer. While it does influence current as a consequence of adjusting the voltage according to Ohm's Law, the primary function is the control of voltage. Unlike some components, it does not measure resistance directly; that function is typically handled by devices like ohmmeters. Additionally, it does not convert electrical energy to mechanical energy, as that description pertains to devices such as motors or actuators.