What is the purpose of capacitors in electrical circuits?

Capacitors play a crucial role in electrical circuits, primarily by storing and releasing electrical energy. When a voltage is applied across a capacitor, it builds an electric field and accumulates energy in the form of an electric charge. This stored energy can then be released back into the circuit when required, allowing capacitors to regulate voltage and supply transient power as needed.

In various applications, capacitors are used to smooth out fluctuations in power supply, filter signals, decouple components in circuits, and provide timing functions. Their ability to quickly discharge energy makes them particularly valuable in applications that require bursts of power or stabilization during unpredictable load changes. This intrinsic property of charging and discharging at specific rates is fundamental to their operation in both alternating current (AC) and direct current (DC) systems.

The other answer choices do not align with the primary purpose of capacitors. Amplifying signals pertains to devices like transistors or operational amplifiers, converting AC to DC involves rectifiers, and measuring voltage is done with devices like voltmeters. Each of those functionalities belongs to other components or systems within electrical engineering.