What is the primary function of a capacitor in electrical systems?

The primary function of a capacitor in electrical systems is to temporarily hold and slowly release voltage. Capacitors are essential components that store electrical energy in an electric field, which allows them to discharge that energy when needed. This characteristic enables capacitors to smooth out variations in voltage and maintain stable power supply in circuits.

When connected to a circuit, the capacitor charges up to the supply voltage, and when the circuit's conditions change, such as during a power supply fluctuation, the capacitor can release the stored energy back into the circuit. This capability makes capacitors crucial for applications like power supply filtering, energy storage, and timing applications in various electronic devices.

In contrast, the other options represent functions not associated specifically with capacitors. For instance, amplifying voltage typically involves amplifiers or transformers, converting AC to DC is the role of rectifiers, and regulating current flow is primarily achieved through resistors and voltage regulators. Each of these components fulfills specific roles that do not relate to the voltage storage and release function of capacitors.