In this article, we are going to learn what is the meaning of capacitor voltage rating and its capacitance value noted in the specification or written on the capacitor body. Also, we will discuss how to choose the capacitance and voltage rating of capacitor. Generally, every capacitor comes with its specification written on its body.

You may notice the following specifications are written on the capacitor body,

Voltage Ratings on Capacitor - 10V, 25V, 35V, 50V, 230V, 400V, etc.

Tolarance - 5%, 10% etc.

Working Temperature - 40, 100 degrees

Anyway, we are going to discuss what voltage rating means of a capacitor.

Polarity - In electrolytic capacitors, negative(-) symbol is given to identify its negative terminal. Although positive terminal is not identified as we can easily identify it once we identified the negative terminal. AC capacitors are have not any polarity identification.

## Capacitor Voltage Rating Means

The voltage rating of a capacitor is meant its maximum operating voltage or working voltage. For example, a capacitor has a voltage rating of 25V, so the capacitor can work properly and safely without any damage up to the maximum voltage of 25V. If we apply more than 25V across that capacitor, it will damage. This maximum working voltage also implies that the capacitor can withstand continuously without any damage. The tolerance indicates the maximum and minimum range from the actual value specified on the capacitor.

Remember that this rated working voltage depends upon the working temperature also. If you applied exactly 25V at the temperature more than its rating then also the capacitor will damage.

Also, remember that the capacitor rated voltage, not the voltage that the capacitor will charge up to. This means if you think a 25V rated capacitor will charge at 25V when it is connected to any power supply, that's wrong. The charging and discharging voltage of the capacitor are depends on the voltage of the power supply to which the capacitor is connected.

When you connect a 25V capacitor with a 9V power supply, then the capacitor will charge up to 9V only not 25V. If you want to charge that capacitor up to 25V then you need a power supply having 25V. But it is not recommended to charge a capacitor up to its working voltage. A 25V capacitor can be charged up to 12V for safe and lifelong operation.

## How to choose the Voltage Rating of Capacitor?

Two things should be kept in mind while choosing the voltage rating of the capacitor - 1. Supply Voltage 2. Working Temperature.

It is best to choose the capacitor voltage rating double of the supply voltage. Don't choose the exact same voltage or less voltage of the capacitor than the power supply voltage.

For example, if you are going to select a capacitor for a 12V circuit, then the suitable voltage rating for the capacitor will be 15V to 25V. You can select more than a 25V capacitor but don't take the capacitor below 15V. Choosing a high value of voltage capacitor gives more safety, reduces the chances of failure, makes it operate long life, etc.

Generally, we don't need to give attention to the temperature rating, because all the capacitors available in the market are suitable for a normal circuit at normal working temperature. But, if you choosing a capacitor for a very high working temperature then you must give attention to the temperature rating. You cannot use normal capacitor designed for general electronic circuit only. The capacitors are specially designed that will be used in High temperature environment.

## Capacitor Voltage VS Capacitance Value

Capacitor voltage and capacitance both are independent of each other. Capacitor voltage rating ensures its maximum working voltage without any damage whereas the capacitance value indicates how much energy a capacitor can store. Capacitor working voltage does not change with frequency but the capacitance value change with frequency and temperature.

So, the conclusion is the capacitance value of a capacitor indicates how much electrical energy can store and the voltage rating indicates the maximum safe voltage at which the capacitor can store energy properly. Also, remember that there are different capacitors for used in AC and DC circuits. AC and DC capacitors are not the same.