Capacitors are able to store electrical charge. The ability of a capacitor to store charge is known as its capacitance, which is measured in Farads. A capacitor consists of two conducting plates separated by an insulator. The factors that affect a capacitor's capacitance include the size of its plates, the distance between plates, and the material between the plates. When choosing a capacitor, its capacitance value, voltage rating, and polarity must all be considered. Capacitors can be connected in series or parallel, with capacitance adding or reducing depending on the configuration.

1. Capacitance/Capacitors

2. CapacitanceCapacitance is the ability of a dielectric (insulator) to store an electrical chargeCharge = Coulomb = Q = 6.25 X 1018 electrons

3. CapacitorsA capacitor is a component that stores electrical chargeSchematicMake up of a capacitorThe unit of measurement for capacitance is the Farad+-Non-Polarity SensitivePolarity Sensitive2 Conducting PlatesDielectric (Insulator)Note to teacher: charge up a 470 µF cap to 30v and then discharge

4. Farad1 Farad: when 1 coulomb is stored in a dielectric with a potential of 1 volt1 Farad is a very large valueTypical values of capacitance are in: microfarads (μF) (10-6) picofarads (pF) (10-12) Higher farad value = more stored chargeNote: Charge up 470 μF and 1000 μF to show differenceQC=VCoulombFarad=Volt1 Volt1 coulomb

5. How Capacitors WorkChargingStoring a chargeDischargehttp://micro.magnet.fsu.edu/electromag/java/capacitor/index.html

6. Factors affecting Capacitance: The ability of a capacitor to store electrical charge (capacitance size) depends upon Size (surface area) of the platesLarger plate area = more capacitanceDistance between the platesCapacitance increases as the width decreasesDielectric MaterialAir = 1Paper = 2-6Ceramics = 80 – 1200Mica = 3-8Mylar = 2-3Electrolytic = 7http://micro.magnet.fsu.edu/electromag/java/capacitance/index.html200 μF100 μF200 μF100 μF

7. Three Important Facts When Choosing a CapacitorCapacitance ValueVoltage RatingPolarity

8. Capacitance ValueRules of thumb (as in 99% of the time)MF or mF on an old capacitor = µF .If a capacitor has a value of 1 µF or more it is usually an electrolytic (canister) capacitor. Conversely, if the capacitance value is less than 1 µF it is usually a disc or chicklet variety.

9. .047 k.1 ZCapacitance Values of Disc CapacitorsThe value of the disc capacitors is usually given in one of two methods. The capacitance value is sometimes printed on the face of the disc capacitor like the following. If this is done then the value of the capacitance is given in micro farads (µF).

10. Capacitance Values of Disc CapacitorsThe capacitance value is sometimes printed in code on the face of the disc as shown below. If this is the case then the capacitance value is given in picofarads (pF). The code given is the same as the code used to determine resistor values. For example: 102 would represent 1= 1st digit of value, 0 = 2nd digit of value, 2= multiplier (how many zeros) Therefore 102 = 1000 picofarads (pF) or .001 micro farads (µF)

11. Capacitors in Series and ParallelCapacitors in SeriesCapacitors in ParallelIn series the width of the dielectric is additive10 μF10 μFCT = 5 μFNotice that they are exactly opposite of resistors!!!!!!!!10 μF10 μFCT = 20 μFIn parallel the plate surface area is additive

12. Resistor/Capacitor Time Constants