What is indicated by the equivalent series resistance (ESR) in a capacitor?

The equivalent series resistance (ESR) of a capacitor is a crucial parameter that indicates the losses associated with the capacitor under AC conditions. It represents the resistive component of the capacitor's impedance, leading to energy dissipation as heat when an alternating current flows through it. High ESR can result in higher power losses, limiting the capacitor's effectiveness in filtering or decoupling applications.

In practical applications, particularly in power circuits, lower ESR is desirable as it means the capacitor can handle higher ripple currents and perform better in terms of efficiency, leading to improved performance of the overall circuit. This understanding highlights the importance of ESR when selecting capacitors for specific uses, particularly in high-frequency or switching applications.