# What is the capacitance c of this capacitor

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Unformatted text preview: st be on outer surface (a2), so that Qenclosed = 0 Physics 212 Lecture 7, Slide 23 Physics Calculation cross-section +Q A capacitor is constructed from two conducting BB cylindrical shells of radii a1, a2, a3, and a4 and length L (L >> ai). What is the capacitance C of this capacitor ? + + + − − − − − − − − − − − − + + + −−− −−− −−− −−− − − − − + −+ − − − −+ − − − a2 a1 + a4 a3 -Q −+ − + − − + + − − metal − − − + + +++ Q C≡ V metal a2 < r < a3: What is E(r)? (A) 0 (A) (B) 1 Q 4πεo r 2 Why? Gauss’ law: ∫ E ⋅ dA = (C) 1 Q 2πεo Lr Qenclosed εo (D) 1 2Q 1 2Q (E) 2πεo Lr 4πεo r 2 E ⋅ 2πrL = Q εo E= 1 Q 2πε Lr 0 Direction: Radially In Physics 212 Lecture 7, Slide 24 Physics Calculation cross-section +Q + + + − − − − − − − − − − − − + + + −−− −−− −−− −−− − − − − + −+ − − − −+ − − − a2 a1 + a4 a3 -Q −+ − + − − + + − − metal − − − + + +++ A capacitor is constructed from two conducting cylindrical shells of radii a1, a2, a3, and a4 and BB length L (L >> ai). Wh...
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