What is the primary function of a capacitor in an electrical circuit?

The primary function of a capacitor in an electrical circuit is to store electrical energy. Capacitors are designed to accumulate and release electrical charge, allowing them to maintain a reservoir of energy that can be used when needed. This capability is essential in various applications, such as filtering signals, managing power supply stability, and providing bursts of energy when demand exceeds the immediate supply.

When a capacitor is connected to a power source, it charges, accumulating energy in the form of an electric field between its plates. When the circuit requires energy, the capacitor can discharge, providing that stored energy. This attribute is particularly useful in HVAC systems, where capacitors are often employed to help start and run electric motors, ensuring they operate smoothly and efficiently.

In contrast, the other options pertain to functions not typically associated with capacitors. Measuring current is the role of ammeters, converting AC to DC is performed by rectifiers, and increasing circuit resistance is characteristic of resistive components, not capacitors.