Ch 21 Practice Pr soln

Ch 21 Practice Pr soln - Chapter 21 Practice Pr solns...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

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

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

Unformatted text preview: Chapter 21 Practice Pr solns: # 22,25,27,29, 30 ,31, 35, 36, 41, 47, 48, 59 22.(a) When the surface is perpendicular to the field, its normal is either parallel or anti-parallel to . E r Then Equation 21.1 gives 2 2 cos(0 or 180 ) (850 N/C)(2 m ) 1.70 kN m /C. E A EA Φ = ⋅ = ° ° = ± = ± ⋅ r r (b) cos(45 or 135 ) E A EA Φ = ⋅ = ° ° = r r 2 2 (1.70 kN m /C)(0.866) 1.20 kN m /C. ± ⋅ = ± ⋅ (c) cos90 0. EA Φ = ° = 25. I NTERPRET This problem is about the electric flux through the surface of a sphere. D EVELOP The general expression for the electric flux Φ is given by Equation 21.1: cos , E A EA θ Φ = ⋅ = r r where θ is the angle between the normal vector A r and the electric field . E r The magnitude of the normal vector A r is 2 4 , A r π = the surface area of the sphere. E VALUATE For a sphere, with E r parallel or anti-parallel to , A r Equation 21.1 gives 2 2 2 4 4 (0.1 m/2) (47 kN/C) 1.48 kN m /C r E π π Φ = ± = ± = ± ⋅ 27. I NTERPRET This problem is about applying Gauss’s law to find the electric flux through a closed surface. D EVELOP Gauss’s law given in Equation 21.3 states that the flux through any closed surface is proportional to the charge enclosed: enclosed q E dA ε Φ = ⋅ = r r r E VALUATE For the surfaces shown, the results are as follows: (a) enclosed ( 2 ) , q q q q = + - = - / . q ε Φ = - (b) enclosed ( 2 ) ( ) 3 ( 3 ) 2 q q q q q q q = + - + - + + - = - and 2 / . q ε Φ = - (c) enclosed q = and 0. Φ = (d) enclosed 3 ( 3 ) q q q = + - = and 0. Φ = A SSESS The flux through the closed surface depends only on the charge enclosed, and is independent of the shape of the surface. 29. I NTERPRET This problem is about applying Gauss’s law to find the electric flux through the surface of a cube which encloses a charge....
View Full Document

This note was uploaded on 06/03/2010 for the course PHYS 299 taught by Professor Hoston,amahd,bakanowski during the Summer '08 term at University of Louisville.

Page1 / 4

Ch 21 Practice Pr soln - Chapter 21 Practice Pr solns...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online