Capacitors

© 2011 Project Lead The Way, Inc.Magic of Electrons

Capacitors

• Capacitors• Charging the Capacitor• Discharging the Capacitor

This presentation is intended to be used with Activity 6.2.5 Capacitors.

CapacitorsCapacitor: An electrical device used to store electrical charge

Symbol for Circuit Diagrams

or

DC

Capacitors

Capacitors allow current to flow through a circuit as they fill with a charge.

When the capacitor’s voltage supply matches the power source, current stops flowing.

DC_

+

Capacitors

• Made of two layers of conductor and a layer of insulator.

• Electrolytic Capacitors

• Capacitance, measured in Farads (F)– 1 F = 6.28 x 1018 electrons– 1 µF = 6.28 x 1012 electrons

Capacitors

• Stored energy in the capacitor is released in a quick burst unless slowed by resistance.

• Capacitors are found in almost all electronic devices.– They store energy, provide quick bursts of power, even out power if there is a small loss, etc.

• Capacitors are used for the flash in cameras.

Charging CircuitDraw a schematic diagram of the following charging circuit, which includes a capacitor, a push switch, a LED, powered by a 6V DC power supply.

Just as an LED is polarity-sensitive, many capacitors are too. Look for an indication on the capacitor to verify.

Discharging CircuitDraw a schematic diagram of the discharging circuit with a pushbutton switch, a LED, and a place for the charged capacitor to be placed.

Will the polarity of the capacitor affect this circuit? Explain.

Charging the Capacitor

Place the smallest capacitor in the circuit. Push the switch, completing the circuit.

What did the LED do after the capacitor was plugged in?

Discharging the CapacitorPlug the capacitor into the discharge circuit. Press the push switch.

What did the LED do?

Repeat the charge and discharge with the other capacitors provided.

Image Resources

Microsoft, Inc. (2009). Clip Art. Retrieved January 22, 2009, from http://office.microsoft.com/en-us/clipart/default.aspx