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Unformatted text preview: Prof. Filippo Capolino ECE Dept. Fall 2006 Notes 23 ECE 2317 ECE 2317 Applied Electricity and Magnetism Applied Electricity and Magnetism Notes prepared by the EM group, University of Houston . (used by Dr. Jackson, spring 2006) Capacitance Capacitance capacitor [ ] F Q C V = [ ] [ ] ( ) 1 F 1 C/V = C [F] +Q -Q +- V r ε A B Note: the “A” conductor has the positive charge. Q = Q A V = V AB Capacitance Capacitance ( ) dQ i dt d Cv dt dv C dt = = = Note: Q is the charge that flows from left to right, into plate A +Q -Q + + + +---- i i +- v ( t ) A B Capacitance Capacitance So ( ) dv i t C dt = “passive sign convention” i i +- v ( t ) Example Example Method #1 (start with E ) “ideal parallel plate capacitor” A B x h [m] A [m 2 ] r ε Assume: ¡ x E x E = B h h AB x x A x V V E dr E dx E dx E h = = ⋅ = = = ∫ ∫ ∫ Find C E x Example (cont.) Example (cont.) Hence ¡ ¡ ¡ A A s A r r r x r x Q A A D n A n E A x E AE AE ρ ε ε ε ε ε ε ε ε = = ⋅ = ⋅ = ⋅ = = r x x AE Q C V E h ε ε = = h [m] A B x A [m 2 ] r ε + + + + + + + + + + + A s ρ [ ] r A C F h ε ε ⎛ ⎞ = ⎜ ⎟ ⎝ ⎠ Example (cont.) Example (cont.) Method #2 (start with...
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This note was uploaded on 10/25/2011 for the course ECE 2317 taught by Professor Staff during the Fall '08 term at University of Houston.
- Fall '08