Capacitors and resistors are two fundamental electronic components that serve opposite functions in circuits. A resistor opposes the flow of electric current and converts electrical energy into heat, with its resistance measured in ohms (Ω). A capacitor stores electrical energy in an electric field between two conductive plates and releases it when needed, with its capacitance measured in farads (F).
In practical terms, resistors work the same way regardless of whether current is constant (DC) or alternating (AC)—they simply dissipate energy. Capacitors, however, behave very differently: they block DC current once fully charged but allow AC current to flow, making them useful for filtering and signal processing. A resistor's opposition to current remains constant, while a capacitor's impedance depends on the frequency of the current.
Resistors are used to limit current flow, divide voltage, set the timing of circuits, and protect components from overcurrent. Capacitors are used to store temporary electrical charge, filter out unwanted signals, smooth out voltage fluctuations, and couple or block different frequency components in circuits. In terms of construction, resistors are typically made from carbon film or wire wound around an insulating core, while capacitors consist of two metal plates separated by an insulating material called a dielectric. Together, resistors and capacitors form the basis of countless electronic circuits, often working in tandem to control how electricity flows and behaves.