When Does A Capacitor Discharge

4 min read Jun 26, 2024
When Does A Capacitor Discharge

When Does a Capacitor Discharge?

A capacitor is an essential component in electronic circuits, used to store energy in the form of an electric field. Ideally, a capacitor can store energy indefinitely, but in reality, it will eventually discharge due to various reasons. In this article, we will explore when a capacitor discharges and the factors that influence its discharge.

What Causes a Capacitor to Discharge?

A capacitor discharges when the voltage across it decreases or becomes zero. This can happen due to several reasons, including:

Leakage Current

Capacitors have a small amount of leakage current, which is the flow of electrons from one plate to the other through the dielectric material. This current is usually very small, but it can cause the capacitor to discharge over time.

External Load

When a capacitor is connected to an external load, such as a resistor, inductor, or another capacitor, it will discharge as the load draws energy from the capacitor.

Parasitic Resistance

Capacitors have internal resistance, known as Equivalent Series Resistance (ESR), which can cause the capacitor to discharge. The ESR is the sum of the resistance of the capacitor's electrodes, lead wires, and internal connections.

Dielectric Absorption

Some capacitors, especially those with ceramic or film dielectrics, can exhibit dielectric absorption, which is the ability of the dielectric material to absorb and release electrical energy. This can cause the capacitor to discharge over time.


Capacitors can degrade over time due to aging, which can cause the capacitance value to decrease, leading to a discharge.

Factors That Influence Capacitor Discharge

Several factors can influence the rate of capacitor discharge, including:

Capacitance Value

A higher capacitance value means a slower discharge rate.

Voltage Rating

A higher voltage rating means a slower discharge rate.


High temperatures can increase the discharge rate, while low temperatures can slow it down.


Older capacitors tend to discharge faster than newer ones.

Type of Capacitor

Different types of capacitors, such as electrolytic, ceramic, or film capacitors, have varying discharge rates.


In conclusion, a capacitor discharges due to various reasons, including leakage current, external load, parasitic resistance, dielectric absorption, and aging. The rate of discharge is influenced by factors such as capacitance value, voltage rating, temperature, age, and type of capacitor. Understanding these factors is crucial in designing and building reliable electronic circuits.

I hope this article helps you understand when a capacitor discharges and the factors that influence its discharge.