PHYS 142 Lecture Notes - Lecture 13: Dielectric, Heat Capacity, Electrical Energy
29 Apr 2015
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Phys 142: electromagnetism and optics - lecture 13: capacitance and capacitors part 3. A capacitor can be charged slowly but then can release the energy very quickly. An important medical application of capacitors is the defibrillator. A heart attack or a serious injury can cause the heart to enter a state known as fibrillation in which the heart muscles twitch randomly and cannot pump blood. A strong electric shock through the chest completely stops the heart, giving the cells that control the heart"s rhythm a chance to restore the proper heartbeat. Electric energy stored in a capacitor is associated with the electric field in the capacitor. This relation can be shown through the energy density of the capacitor: If we know the e-field in a region, we can easily calculate the electric energy density in that region. A normal parallel-plate capacitor has the plates separated by a vacuum.
