How to Make a Capacitor Charging Circuit

A flat, dielectric capacitor may be used for this project.

A capacitor is an electrical device that stores electric charge. Capacitors can be used to smooth out direct current (DC) power or can be used to change the characteristics of alternating current (AC) power. A capacitor becomes charged when a voltage differential is applied to the leads of that capacitor. When the voltage differential is removed, the capacitor begins to discharge slowly unless there is a pathway for electric current between the capacitor's leads. A capacitor's charge rate is a direct function of the resistance of the charging circuit.

Things You'll Need

• Electrical wire
• Electrical pliers
• 100-kiloohm resistor
• 1-kiloohm resistor
• 10-microfarad dielectric capacitor
• Voltmeter
• 6-volt lantern battery

Instructions

1. Cut two segments of electrical wire, with each segment being 6 inches long. Strip 1/2 inch of insulating material from the ends of each wire segment.

2. Twist together one end of the first wire with one of the leads from the 100-kiloohm resistor. Twist the free lead from the 100-ohm resistor together jointly with one of the leads from the 1-kiloohm resistor and with one of the leads from the capacitor.

3. Twist together one end of the second wire jointly with the unoccupied lead from the 1-kiloohm resistor and with the unoccupied lead from the capacitor.

4. Attach the red (positive) probe from the voltmeter to the joint where the capacitor, the 100-kiloohm resistor and the 1-kiloohm resistor meet. Attach the black (negative) probe from the voltmeter to the joint where the capacitor, the second wire and the 1-kiloohm resistor meet.

5. Turn on the voltmeter and set the measurement scale to "Volts DC." Attach the loose end of the first wire to the positive battery terminal. Attach the loose end of the second wire to the negative battery terminal, and view the voltmeter display. The capacitor voltage will be 3.78 volts after one second, 5.16 volts after two seconds, and will be fully charged when five seconds have elapsed.

Tips & Warnings

• When power is removed from this circuit, the capacitor will automatically discharge within five seconds.

References

• University of Waterloo (Canada): Capacitor Theory
• The Electronics Club: Capacitance and Uses of Capacitors