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Unformatted text preview: HW-3
1. Find the electric field a distance z above the center of circular disk of radius R which
carries a uniform surface charge density . What does your formula give in the limit
R and R z . 2. Suppose the electric field in some region is found to be E kr3 r , in spherical
coordinates (k is some constant).
(a) Find the charge density .
(b) Find the total charge contained in a sphere of radius R, centered at the origin.
3. Find the electric field inside a sphere which carries a charge density proportional to the
distance from the origin, kr , for some constant k.
4. Two spheres, each radius R and carrying uniform charge densities + and –,
respectively, are placed so that they partially overlap. Call the vector from the positive center to the negative center d . Show that the field in the region of overlap is constant,
and find its value. 5. Find the potential a distance r from an infinitely long straight wire that carries a uniform
line charge . Compute the gradient of your potential and check that it yields the correct
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This note was uploaded on 02/06/2010 for the course PHYSICS 11 taught by Professor Qiu during the Fall '09 term at Berkeley.
- Fall '09