What is an RC circuit primarily composed of?

An RC circuit is primarily composed of a resistor and a capacitor. In such circuits, the resistor limits the current flow and determines the time constant of the circuit, while the capacitor stores electrical energy. The interaction between these two components gives rise to important circuit behaviors, such as charging and discharging characteristics, and is crucial in applications like filtering, timing, and waveform shaping.

When a voltage is applied to an RC circuit, the capacitor begins to charge through the resistor. The rate at which the capacitor charges is determined by the time constant, which is the product of resistance and capacitance (τ = R × C). This time constant defines how quickly the circuit responds to changes in voltage. In practical terms, the resistor and capacitor together form the backbone of many electronic circuit designs, including those in audio equipment, signal processing, and timing applications.

In contrast to the other options, which involve different combinations of electrical components, the pair of resistor and capacitor is unique to RC circuits and directly indicates their foundational function and behavior.