Lecture+09+feb2

Lecture+09+feb2 - Exam Locations: Gidley 9 am section 100:...

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Unformatted text preview: Exam Locations: Gidley 9 am section 100: A-K 170 Denn L-Z 182 Denn Lecture #9 Energy storage in Capacitors Dielectrics Energy stored in a capacitor (Demo: The Killer Capacitor) Separating + from - charge requires work by an external force: Moving charge Q through V =V requires U = W ext = QV (NOT HERE!) (This is indeed the work done by the battery!) But V of capacitor builds up as q builds up: V = q/C Thus, dU = Vdq = dW ext = (q/C)dq 2 2 2 2 1 2 1 2 1 2 1 CV QV C Q C q C qdq Vdq U Q Q q Q q = = = = = = = = So why the factor of here??? Question #1>>>>> Question #1 The work done by the battery to transfer Q from one conductor of the capacitor to the other is QV. The energy stored in the capacitor is only ()QV. So what happened to the other (1/2)QV of energy? A. Light generated while charging B. Heating of the connecting wires C. Energy is not conserved for moving charges D. It went into dark energy of the universe E. Kinetic energy of the capacitor Storing Energy in the E Field...
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This note was uploaded on 02/15/2012 for the course PHYS 240 taught by Professor Winn during the Winter '11 term at University of Michigan.

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Lecture+09+feb2 - Exam Locations: Gidley 9 am section 100:...

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