Ch17 HW4 - 12/17/10 9:14 PM Ch17 HW4 F2010 Page 1 of 5

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Unformatted text preview: 12/17/10 9:14 PM Ch17 HW4 F2010 Page 1 of 5 http://www.webassign.net/v4cgisacoreth@ncsu/student.pl?u=20101218021414sacoreth@ncsu6657124101 Current Score : 30 / 30 Due : Wednesday, September 22, 2010 11:25 AM EDT 1. 4/4 points Question: MI3 17.7.P.094.alt01 A highly charged piece of metal (with uniform potential throughout) tends to spark at places where the radius of curvature is small, or at places where there are sharp points. The breakdown electric field strength for air is about 3 10 6 V/m. (a) It is possible to calculate the maximum possible potential (relative to infinity) in air of a metal sphere of 9 cm radius. First, what is the maximum charge you can put on this sphere? 2.7e-6 2.70e-06 C For that amount of charge, what is the potential of the sphere relative to infinity? 270000 2.70e+05 volts (b) Next, calculate the maximum possible potential relative to infinity in air of a metal sphere of only 0.2 mm radius. What is the maximum charge you can put on this sphere? 1.33e-11 1.33e-11 C For that amount of charge, what is the potential of the sphere relative to infinity? 600 600 volts These results are related to the fact that if a piece of metal has a small radius of curvature, it will spark at relatively low potential relative to infinity. Solution or Explanation At the surface of the sphere, E = 3e6 V/m. Solve for q, then find V at the surface of the sphere. 2. 7/7 points Question: MI3 17.6.P.082 Ch17 HW4 F2010 (Homework) Stefan Coreth PY 208, section 002M, Fall 2010 Instructor: Laura I. Clarke Web Assign The due date for this assignment is past. Your work can be viewed below, but no changes can be made. 12/17/10 9:14 PM Ch17 HW4 F2010 Page 2 of 5 http://www.webassign.net/v4cgisacoreth@ncsu/student.pl?u=20101218021414sacoreth@ncsu6657124101http://www....
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Ch17 HW4 - 12/17/10 9:14 PM Ch17 HW4 F2010 Page 1 of 5

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