Phys208 09F 1st exam
Sunday, September 27, 2009
10:46 AM
1. (20 pts) If a = 3.0 mm, b = 4.0 mm, Q1 = Q2 = 60 nC, and q = 32 nC in the figure, what is the
magnitude of the total electric force on q?
2.
(20 pts) A 16-nC charge is distributed uniformly along the x axis from x = 0 to x = 4 m. Calculate the electric field at x = +10 m
on the x axis?
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3 (30pts) An conducting sphere of radius R1 is placed at the center of a grounded and
conducting spherical shell of inner and outer radii of R2 and R3. The solid sphere carries a charge
q1.
(1) (4pts) Calculate E(r) and V(r) at r>R3
(2) (6 pts) Calculate E(r) and V(r) at R3 > r>R2.
(3) (8 pts) Calculate E(r) and V(r) at R2 > r>R1.
(4) (12 pts) Calculate E(r) and V(r) at R1>r .
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4 (30pts) An conducting cylinder of radius R1 is placed at the center of a conducting cylindrical shell of inner and outer radii
of R2 and R3. The solid cylinder and cylindrical shell carry a charge density λ1 and λ2 (in unit of C/m), respectively.
(You will lose credit if you just write down the answers, you have to show your work)
(1) (10 pts) Calculate E(r) at r>R3.
(2) (10 pts) Calculate E(r) at R2 > r>R1
(3) (10 pts) Calculate the potential difference between two charged cylinders.
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