PHYS 308 Homework
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   Homework #3: Due Friday, February 13, by 5:00pm.

  1. Here are two charges and their locations: (-)22μC located at the point (x,y)=(0.90m, 1.30m); (+)22μC located at the point (x,y)=(-1.25, -3.00m). Use Mathematica to plot both the electric field vectors and the electric field unit vectors due to these charges. You are to plot this in the range x=-4.0m to 4.0m and y=4.0m to 4.0m. It should go without saying that both of these charges are present--this isn't two separate one-charge situations.
  2. A solid sphere of radius 90cm has a non-uniform change density given by ρ=ρ0r3 where ρ0=(+)5.60μC/m6. If a hole of radius 12.0cm is carved in the center of the sphere , find the magnitude of the electric field at a radius of (a) 72cm, and (b) 110cm.
  3. Here is an electric field vector: E=xExx3y2 + yEyxy4. Here, Ex=1,200 N/C/m5 and Ey=1,700 N/C/m5. (a) Find the electric potential difference (voltage) between the points (-1.70m, 3.40m) and (4.50m, 3.40m). (b) Find the electric potential difference (voltage) between the points (-1.70m, 3.40m) and (-1.70m, -3.40m).
  4. Exercise 2.31 in the text. Ignore the last sentence in this problem, the one that starts with "Take the gradient..." In other words, don't take the gradient of anything. Note that the book advises you that they have left out the constants that take care of the units--they are aware of units, but they are trying to make things clean for you at first.
   That's all for homework #3.