How to Charge a Capacitor
Charging a capacitor is very simple. A capacitor is charged by connecting it to a DC voltage source. This may be a battery or a DC power supply.
Once the capacitor is connected to the DC voltage source, it will charge up to the voltage that the DC voltage source is outputting. So, if a capacitor is connected to a 9-volt battery, it will charge up to 9 volts. If a capacitor is connected to a DC power supply outputting 15 volts, it will charge up to 15 volts. All that has to be done is for the positive side of the DC voltage source to be connected to the positive side of the capacitor, the longer lead, and the negative side of the DC voltage source be connected to the negative side of the capacitor, the shorter lead.
Below is the circuit of how a capacitor is charged:
In this case, the capacitor charges up to 9 volts, since it's connected to a 9-volt battery. Many of the times while charging a capacitor, a resistor is used in series with the capacitor and voltage source to decrease the amount of current that flows through the capacitor, so that the capacitor isn't damaged. This is usually recommended.
Note: Only charge a capacitor to or below its specified voltage rating. Charging a capacitor to a voltage beyond its voltage rating can destroy the capacitor. To find more information about a capacitor's voltage rating, check out What Does the Voltage Rating On a Capacitor Mean?.
We have just demonstrated how to charge a capacitor but we haven't done anything useful with the charged capacitor. Click on How to Use a Charged Capacitor to Light an LED to learn how to do useful things with a charged capacitor. This projects shows you how you can use a charged capacitor to turn on a load such as light an LED.