Notes on Chapter 25

# Notes on Chapter 25 - Chapter 25 Capacitance 25-1 A...

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17 June 2010 1 Chapter 25 – Capacitance A capacitor is a device in which electrical energy can be stored 25-1

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17 June 2010 2 Capacitance Basic elements of a capacitor 25-2 Parallel-plate capacitor
17 June 2010 3 Circuit symbols for capacitor Examples of capacitors

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17 June 2010 4 The charge q on the plates is found to be proportional to the potential V for a capacitor q CV = C is called the capacitance of the capacitor with a value that is determined by the geometry of the capacitor SI unit of C is the farad 1 / farad F coulomb per volt C V = = = Since the farad is a very large unit (we show this later), it is more practical to use submultiples of the farad: 1 microfarad ( 1 μ F = 10 -6 F ) 1 nanofarad ( 1 nF = 10 -9 F ) 1 picofarad ( 1 pF = 10 -12 F )
17 June 2010 5 Charging a Capacitor

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17 June 2010 6 Calculation of Capacitance Consider the Gaussian surface shown 0 () EA q A ε = Assuming is uniform and and are parallel f i fi V V E ds = −⋅ E A . ( )cos180 E ds Eds Eds = °=− B V V V Eds + = −= Choose a path whose direction is opposite that of the electric field, that is, from the negative to the positive plate in the figure 25- 3 E q A d E o = .
17 June 2010 7 Apply Equations (A) and (B)

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## This note was uploaded on 09/30/2010 for the course PHYS MTH 203 taught by Professor None during the Spring '10 term at American University of Sharjah.

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Notes on Chapter 25 - Chapter 25 Capacitance 25-1 A...

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