# what q a a area of plate second integrate e to find

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Unformatted text preview: charged conductors: +Q y d σ E= εo E x -Q What is σ ?? What ?? Q σ= A A = area of plate Second, integrate E to find the potential difference V d d 0 V = − ∫ E ⋅ dy d 0 V = − ∫ (− Edy) = E ∫ dy = 0 Q d εo A As promised, V is proportional to Q !! 12 Q Q C≡ = V Qd / ε o A C= ε0 A d C determined by determined geometry !! geometry Physics 212 Lecture 7, Slide 12 Physics Question Related to Preflight +Q0 Initial charge on capacitor = Q0 BB d - Q0 +Q1 Insert uncharged conductor Charge on capacitor now = Q1 d t - Q1 How is Q1 related to Q0 ?? A. Q1 < Q0 B. Q1 = Q0 C. Q1 > Q0 14 Plates not connected to anything CHARGE CANNOT CHANGE !! Physics 212 Lecture 7, Slide 13 Physics Where to Start?? +Q0 d t BB - Q0 What is the total charge induced on the bottom surface of the conductor? A. B. C. D. E. 17 +Q0 -Q0 0 Positive but the magnitude unknown Negative but the magnitude unknown Physics 212 Lecture 7, Slide 14 Physics WHY ?? +Q0 E - Q0 E=0 +Q0 E - Q0 WHAT DO WE KNOW ??? E must be = 0 in conductor !! Charges inside conductor move to cancel E field from top & bottom plates 19 Physics 212 Lecture 7, Slide 15 Physics Calculate V y Now calculate V as a function o...
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## This note was uploaded on 02/09/2012 for the course PHYSICS 212 taught by Professor Mestre during the Spring '11 term at University of Illinois at Urbana–Champaign.

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