A2 a1 metal what is the capacitance c of this device

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: nducting cylindrical shells of radii a1, a2, a3, and a4 and length L (L >> ai). a2 a1 metal What is the capacitance C of this device ? metal • Conceptual Analysis: Q C≡ But what is Q and what is V? They are not given?? V • Important Point: C is a property of the object!! (concentric cylinders here) • Assume some Q (i.e., +Q on one conductor and –Q on the other) • These charges create E field in region between conductors • This E field determines a potential difference V between the conductors • V should be proportional to Q; the ratio Q/V is the capacitance. 33 Physics 212 Lecture 7, Slide 20 20 cross-section a4 a3 Calculation A capacitor is constructed from two conducting cylindrical shells of radii a1, a2, a3, and a4 and length L (L >> ai). a2 a1 metal metal What is the capacitance C of this capacitor ? Q C≡ V • Strategic Analysis: – – – – Put +Q on outer shell and –Q on inner shell Cylindrical symmetry: Use Gauss’ Law to calculate E everywhere Integrate E to get V Take ratio Q/V: should get expression only using geometric parameters (ai, L) Physics 212 Lecture 7, Slide 21 21 Calculation cross-section +Q + + + + + + + + + a2 a1 + a4 a3 -Q + + + + metal + + + + + metal A capacitor is cons...
View Full Document

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.

Ask a homework question - tutors are online