What is the primary role of a resistor in a circuit?

The primary role of a resistor in a circuit is to limit the flow of electric current. This is achieved by providing a specified amount of resistance to the flow of electrons, which in turn controls the current according to Ohm's Law. Ohm's Law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor (I = V/R).

By introducing resistance into the circuit, resistors help protect sensitive components from excessive current, divide voltage levels, and manage heat dissipation within the circuit. Their value is measured in ohms, and they are essential for fine-tuning circuit behavior, ensuring that devices operate within their specified current ranges.

Other options, while relevant to various electronic components, do not represent the fundamental purpose of a resistor. For instance, storing energy in a magnetic field pertains more to inductors, changing the voltage level of AC relates to transformers, and measuring voltage and current is typically the function of multimeters. Thus, the function of a resistor is distinctly identified by its ability to limit current flow within electrical circuits.