What is a capacitor used for in electronic circuits?

A capacitor is primarily utilized in electronic circuits to store electrical energy temporarily. This ability to store and release energy makes capacitors vital components in various applications. For instance, in power supply systems, capacitors can smooth out voltage fluctuations, providing a more stable output by temporarily holding charge during peak loads.

Additionally, in timing circuits, capacitors can control the timing functions by determining the charge and discharge rates, which directly affect the frequency of oscillation in the circuit. The stored energy can be released when needed, enabling the circuitry to perform functions such as filtering noise in power supplies or coupling and decoupling AC signals.

While other options mentioned in the question touch on important components of electronic circuits, they do not directly align with the fundamental role of a capacitor. The conversion of AC to DC typically involves diodes and rectifiers rather than capacitors. Increasing signal strength is generally achieved using amplifiers. Measuring voltage fluctuations is performed using devices like voltmeters or oscilloscopes, not capacitors.