What is the primary use of a capacitor in AC circuits?

A capacitor in AC circuits primarily serves to store electrical energy in an electric field. This storage capability allows capacitors to manage energy flow and improve circuit performance in several ways. In AC systems, the voltage continuously changes, leading to the charge being absorbed and released by the capacitor. This action helps to smooth out fluctuations in the supply voltage and assists in maintaining consistent current levels.

Additionally, capacitors play a significant role in phase shifting, helping to adjust the timing of the current flow in relation to the voltage. This is particularly important in applications like motors, where a capacitor helps create a phase difference necessary for the motor to start and run efficiently.

When examining other options: limiting current typically relies on resistors or circuit protection devices rather than capacitors. Providing mechanical support is not a function of capacitors, as they are electrical components without structural support roles. Reading voltage levels is generally accomplished with measuring instruments, not with the function of a capacitor.

Thus, the main reason the primary use of a capacitor in AC circuits is to store charge is firmly based on its ability to manage energy and improve the stability and efficiency of electrical systems.