How to Charge a Capacitor

A capacitor usually consists of two conductors placed close to each other. It stores electrical charge in units that are called a farad. Common capacitor values typically range from picofarads to nanofarads to microfarads.

To charge a capacitor, you only need to attach it directly to a power source. Since this will charge it almost immediately, use a resistor to slow this charging time down. Also, to measure the voltage of the capacitor before, during, and after discharging, use a multimeter.

Difficulty: Moderate

Instructions

Things You'll Need:

• Battery with battery holder Switch Capacitor Resistor or potentiometer Multimeter Wire

1. Connect one end of the battery holder to the switch. Make sure the switch is open (in the up position).

2. Attach a resistor to the other end of the switch.

3. Secure one end of a capacitor to the resistor, and the other end of the capacitor to the unoccupied terminal of the battery holder.

4. Change the settings on the multimeter to that of voltage. Place one lead across one end of the capacitor and the other lead across the other end of the capacitor. You may need to find it necessary to use extra wires to hold the leads in place.

5. Place a battery inside the battery holder, and close the switch. Observe the values on the voltmeter. The charge on the capacitor should b approximately equal to that of the voltage from the power.

6. To discharge the capacitor quickly, replace the battery with a wire. Do not touch the capacitor directly. Again, observe the values on the voltmeter. It will decrease in time to approximately zero.

Tips & Warnings

• When wiring the circuit, be sure to observe polarity if you are using an electrolytic or other polarized capacitor. The positive terminal of the capacitor must be connected to the positive terminal of the battery, and the negative terminal of the capacitor must be connected to the negative terminal of the battery.
• Capacitors can retain electrical charge for long periods of time even when they are not directly connected to a power source, so use extreme caution when handling one. High voltage capacitors found in electronics such as television sets, camera flashes, and radios, for example, may contain large amounts of voltage that may be lethal.

Resources

• Capacitor Safety FAQ