# HW 11 - terry (ect328) homework 11 Turner (59130) 1 This...

This preview shows pages 1–3. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

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

Unformatted text preview: terry (ect328) homework 11 Turner (59130) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A long coaxial cable consists of an inner cylin- drical conductor with radius R 1 and an outer cylindrical conductor shell with inner radius R 2 and outer radius R 3 as shown. The ca- ble extends out perpendicular to the plane shown. The charge on the inner conductor per unit length along the cable is and the corresponding charge on the outer conductor per unit length is- (same in magnitudes but with opposite signs) and > 0. Q R 1 R 2 R 3 b- Q Find the magnitude of the electric field at the point a distance r 1 from the axis of the inner conductor, where R 1 < r 1 < R 2 . 1. E = 2 r 1 2. E = 0 3. None of these. 4. E = 2 R 1 4 r 1 2 5. E = 2 r 1 correct 6. E = R 1 3 r 1 2 7. E = 3 r 1 8. E = R 1 4 r 1 2 9. E = 2 3 r 1 10. E = 2 R 1 Explanation: Pick a cylindrical Gaussian surface with the radius r 1 and apply the Gausss law; we obtain E 2 r 1 = Q E = 2 r 1 002 (part 2 of 2) 10.0 points For a 100 m length of coaxial cable with inner radius 0 . 618954 mm and outer radius 1 . 83396 mm. Find the capacitance C of the cable. Correct answer: 5 . 12174 nF. Explanation: Let : = 100 m , R 1 = 0 . 618954 mm , and R 2 = 1 . 83396 mm . We calculate the potential across the capaci- tor by integrating-E d s. We may choose a path of integration along a radius; i.e.,-E d s =-E dr . V =- 1 2 q l integraldisplay R 1 R 2 dr r =- 1 2 q l ln r vextendsingle vextendsingle vextendsingle vextendsingle R 1 R 2 = q 2 l ln R 2 R 1 . Since C = q V , we obtain the capacitance C = 2 l ln parenleftbigg R 2 R 1 parenrightbigg = 2 (8 . 85419 10 12 c 2 / N m 2 ) ln parenleftbigg 1 . 83396 mm . 618954 mm parenrightbigg (100 m) = 5 . 12174 nF . terry (ect328) homework 11 Turner (59130) 2 003 10.0 points Given a spherical capacitor with radius of the inner conducting sphere a and the outer shell b . The outer shell is grounded. The charges are + Q and- Q . A point C is located at r = R 2 , where R = a + b . a A B C + Q- Q b What is the capacitance of this spherical capacitor?...
View Full Document

## This note was uploaded on 02/17/2010 for the course PHY 59130 taught by Professor Turner during the Fall '09 term at University of Texas at Austin.

### Page1 / 7

HW 11 - terry (ect328) homework 11 Turner (59130) 1 This...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online