Capacitors and Capacitance 10 20 14 9 19 AM Provide a method for controlled release and storage of charges Definition of Capacitor Any set of two conductors holding equal and opposite charges q and q net charge on a capacitor is always zero We define charge on capacitor as the magnitude of charge on one of the conductors so in the problem only charge will be given and the system will be identified as a capacitor or as two equal and opposite conductors Examples of capacitors Properties Positive and negative bodies are both conductors which implies that positive and negative potential are constant over respective conductor Electric field E lines emerge from positive and disappear into negative conductor move from positive to the negative Positive potential on conductor with charge q is greater than the negative potential on conductor with charge q assuming you define V final at any arbitrary point it will happen in the exact center equidistant from parallel and opposite plates Example Electric field will change to compensate for a different path but Always constant irrespective of path change in voltage is CONSTANT Definition of capacitance Ability to store charge C capacitance charge that a capacitor can hold per unit potential difference in between the conductors Units are charge per potential Coulombs per volts defined as Farads F Typically Capacitance depends only on the geometry of conductors area shape size Example One Parallel Plate Capacitor Now finding the potential so we are going to go from top to bottom Example 2 one conducting sphere inside another spherical capacitor Cylindrical Case Special cases o Combination of capacitors Two basic cases to add together series and parallel Series C effective microfarads o o Parallel C effective 4 microFarads add linearly C effective C1 C2 C3 Cn o o Note o What happens when you charge a capacitor Energy storage in a capacitor
View Full Document
Unlocking...