Discuss Bill Compton's answer to: Physics

Capacitors are essential electrical and electronic components, use to store charges, shift phase of applied voltage, block DC and pass AC.  Depending on the construction and size of the capacitor, capacitors may range from 20 nm on microprocessors to the size of a two story building used at power generating stations.  Capacitors are rated in Farads, after the physicist who first rendered capacitors practical, Michael Faraday. 

Capacitors operate on diamagnetic induction: some materials have a greater diamagnetic potential than others and find greater use in capacitors.  Aluminum is one of these materials, although we may also use germanium arsenide and silicon arsenide as semiconductor capacitors.  For the present discussion, let us study dielectric capacitors. 

Note that line voltage is scalar (which operates in small “steps” as one might scale a ladder) and plate voltage is planar, having no “steps” to scale, operating at 900 to the plates.  Hence we see an uneven distribution of charge through the plates.  That will become important as we discuss capacitance.

Faraday’s First Law states that: “Capacitors connected in series have an inverse phase relationship offset by 90 degrees per capacitor, and equal wattage where the smallest of the capacitors will charge to the highest voltage and deliver the least current on discharge.”  In this example, we will apply a scalar line voltage of 10,000 VAC 60 Hz. 

Parallel capacitance: C/1, C/2, C/3 = C total. 

                                                                                                                        Note that capacitors tied in series add

                                                                                                       as resistors tied in parallel, and wattage

                                                                                                                        remains constant.   The smallest capacitor

C1                 C2               C3                                         will fail first and worst.

         100mf         1,000mf      10,000mf
         90deg          180deg        270deg  
         10,000V         1,000V         100V

Faraday’s Second Law states that: “Capacitors connected in parallel have a direct phase relationship and an inverse voltage potential.”  Here the largest capacitor bears the brunt and the smallest capacitor faces the lightest load.  Capacitors tied in parallel add as resistors tied in series.

                                                                                                                                Note that capacitors tied in parallel

                                                                                                                                add as resistors tied in series.

                                                                                                                                Phase changes 90deg. 

                       C1                    C2                           C3
                       100mf         1,000mf               10,000mf