Which component is primarily responsible for limiting current flow in a circuit?

The component that is primarily responsible for limiting current flow in a circuit is the resistor. Resistors are designed to provide opposition to the flow of electric current, which allows them to regulate and limit the amount of current that can pass through a circuit. This characteristic is fundamental in protecting sensitive components from excessive current that could potentially cause damage.

When a voltage is applied across a resistor, according to Ohm's Law (V = IR), the amount of current (I) that flows through the resistor is directly proportional to the voltage (V) and inversely proportional to the resistance (R). By manipulating the resistance, one can effectively control the current in a circuit, which is particularly important in various applications such as controlling lights, protecting circuits, or in signal processing.

Other components have different primary functions. A voltage source is responsible for providing the electromotive force required to drive current through a circuit. A transformer is used to change the voltage level in AC circuits without significant loss of power, while a capacitor stores electrical energy temporarily and is more associated with filtering and timing applications rather than directly limiting current flow. Thus, the resistor's role as a current-limiting device is what makes it the correct answer in this context.