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

A resistor limits or controls the flow of electric current in a circuit by providing a specific amount of resistance, measured in ohms. Resistors are used to set current levels, divide voltage, and protect sensitive components from too much current. A capacitor stores electrical charge; a transistor can amplify signals; and a diode (or rectifier) converts AC to DC. Knowing the basic job of each common component — resistor (limits current), capacitor (stores charge), diode (one-way valve), transistor (amplify/switch) — is core electronics content.