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Evidence of Learning 2. Capacitors Resistors Charge Discharge Time constant Energy Stored. Capacitor Features. Capacitance is measured in Farads (F) usually m , n, p Two plates of area ‘a’ separated by a distance ‘d’ Larger plates (a) give higher capacitance
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Evidence of Learning 2 Capacitors Resistors Charge Discharge Time constant Energy Stored
Capacitor Features • Capacitance is measured in Farads (F) usually m, n, p • Two plates of area ‘a’ separated by a distance ‘d’ • Larger plates (a) give higher capacitance • Smaller distance (d) gives larger capacitance • Some capacitors us a special electrolyte to enhance their ability to store charge (electrolytic capacitors) • Other capacitors have a dielectric between their plates, some materials store more charge than others
Dielectric The extent to which any material concentrates electrostatic ‘lines of flux’ • Vacuum has a dielectric constant of 1 (one) • All other dielectrics have a relative value to vacuum and air has dielectric of about 1.00058986 (one) • PTFE: 2.1 • Polystyrene: 2.5 • Glass: 4.7 • Silicon: 11.68 • So you can guess that Silicon makes larger capacitor values for the same size plate area and distance
Series and Parallel • Capacitors in parallel are effectively increasing the area ‘a’ • Capacitors in series are increasing the distance ‘d’ SO THAY: • Capacitors in parallel ADD – the total capacitance is the sum of all the capacitors – always more than the any one of the capacitors…. Ct = C1+C2+…..Cx • Capacitors in series REDUCE – the total capacitance is: