PHY 182 1st Edition Lecture 20Outline of Last Lecture I. How to Calculate Potential DifferenceII. Corona DischargeIII. Equipotential SurfacesOutline of Current Lecture I. Potential EnergyII. Parallel Plate CapacitorsIII. Conductors in EquilibriumCurrent LecturePotential Energy- The equation for potential energy of a capacitor is very similar to the potential energy of a spring. U = .5CV2 = .5QV- Energy per unit of volume is called energy density (u). To calculate this value, divide the potential energy by the volume.- AAA battery = 5000J, AA battery = 9400J- A capacitor of a similar size cannot hold the charge of a battery.- Κ (kappa)=C/C0 this value is called the dielectric constant.- Energy of a capacitor equals E0/K (when Q is constant, can't use this equation for a battery).- Polarization of a dielectric makes a weak opposing electric field.- The voltage across a capacitor is the same as the voltage across a battery.- Capacitance is a measure of the ability of a capacitor to store energy. (Larger capacitors can store more energy.)- SI unit of capacitance is the farad. 1F = 1 C/VThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Parallel Plate Capacitors- When calculating the capacitance of a parallel plate capacitor, we will make the assumption that it is in a vacuum. C=Q/Vab- A farad is a fairly large unit. We will usually use micro, nano, or pico-farads.- Modern technology allows a capacitor the size of a water bottle to have a capacitance of 1 farad. To achieve this, there must be a material between the plates. This material is usually a dielectric.Conductors in Equilibrium- For a conductor in equilibrium, the surface is an equipotential surface, which means that all points inside are at the same potential.- If two conductors are connected with a conducting wire, one equipotential surface is formed.- Any two conductors separated by an insulator form a capacitor. Usually it will be charged with a
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