Lecture 18 - RC circuits

Lecture 18 - RC circuits - RC circuit = circuit with...

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1 Lecture 18 RC circuits RC circuit = circuit with resistors and capacitors. The simplest one: R C ε Charging the capacitor Capacitor initially uncharged. At t = 0, + – – close the switch. + = 0 + : (right after) (0) I Current flows “through” C as through an ideal wire (0) 0 Q +++ ––– Charge builds up on the capacitor’s plates, and C () Qt Vt E battery C ( ) At : () 0  C acts like an open switch After a long time, and charges cannot move. C V Adding charge to the plates is more and more difficult.

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2 Q t () C  (0) 0 R I () 0 (0) ε ACT: Charging a capacitor The capacitor in the circuit below is initially uncharged. What is its charge ( ) a long time after the switch is closed? 1 2 A. ( ) < C B. ( ) = C C. ( ) > C C When the capacitor is fully charged and behaves like an open switch, there is still current in this circuit! 1 12 RR 2 A The potential difference between points A and B is: A B1 2 V VI   B  2 2 CV CIR  
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This note was uploaded on 09/21/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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Lecture 18 - RC circuits - RC circuit = circuit with...

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