A capacitor is an electrical component that stores electric energy by separating two conducting plates with an insulating material called a dielectric. There are different types of capacitors that vary in size, plate arrangement, and dielectric material. Capacitors are used in applications like communications equipment, instruments, computers, and power supplies. The ability of a capacitor to store electric charge is measured in Farads, with the amount of stored charge being proportional to the applied voltage. Capacitors charge by allowing electrons to accumulate on plates when connected to a power source, and discharge the stored energy when connected to another circuit.

1. Electrical & Electronic Components

2. What is a capacitor A passive component designed for storing electric energy (charge) Increases efficiency of a circuit system Does not dissipate heat but stores energy Energy stored can be retrieved at a later time Blocks DC and permits AC to pass

3. Capacitors – electrical components

4. Capacitor types LSU 08/11/2004 Electronics 2 Ceramic disk Monolithic ceramic Dipped siver-mica Mylar Mylar Solid tantalum, polarized Radial aluminum electrolytic Axial aluminum electrolytic

5. Construction Consists of two conducting plates separated by an insulating layer called a dielectric . Differs in size, arrangements of plates and dielectric material

6. Application Communications Instrumentations Life support equipment Computers Power supply systems

7. Capacitance The measure of a capacitor in its ability to store electric charge Expressed in Farads (F) Electric charge stored is proportional to voltage supplied from Power Supply: Q = CE Q = Charge stored C = Capacitance E = Voltage applied to capacitor

8. Charging a capacitor Capacitor not charged yet : Capacitor not connected to power source (battery) No potential difference between plates Therefore no charges stored in capacitor

9. Charging…cont’d Battery connected across capacitor: Electrons flow to and from plates Electrons cannot flow through because of dielectric material Counter emf ( reactance ) induced on plates Electrostatic field induced between plates Reactance level = Power Supply no further flow of current

10. Charging…cont’d Power Supply disconnected: Capacitor retains charges because of electrostatic force existing between plates Unequal charges on both negative & positive plates Capacitor is now a source of potential energy

11. Discharging a capacitor Capacitor connected to other circuit: Electrons flow through from negative plated to positive plate Capacitor is discharging

12. Discharging…cont’d Current will stop flowing when charges of both positive and negative plates are equal Capacitor is fully discharged when there’s no more energy left

13. Capacitors in parallel circuits Able to store more charges C = C1+C2+C3…

14. Capacitors in series circuits Able to store less charges C = (C1xC2) / (C1+C2)