TA: Tomoyuki Nakayama
Thursday, May 27, 2010
PHY 2048: Physic 2, Discussion Section 8701
Quiz 2 (Homework Sets #3 & #4)
Name:
UFID:
Formula sheets are not allowed. Calculators are allowed. Do not store equations in your calculator.
You need to show all of your work for full credit.
________________________________________________________________________________
In the figure below right, a small circular hole of radius
R
= 3.00 cm has been cut in the middle of an
infinite, flat, nonconducting surface that has uniform charge density
σ
= 6.00 pC/m
2
. A z axis, with
its origin at the hole’s center, is perpendicular to the surface. We are going to find out the electric
field at point
P
at
z
= 5.00 cm in a following way:
a) Applying Gauss’s law, find the electric field at point
P
due to the nonconducting surface
before
the hole was cut.
We take our Gaussian surface to be a cylinder which has
end caps of area A parallel to the flat surface. Then the
electric field is perpendicular to the end caps and
parallel to the round surface of the cylinder. Gauss’s law yields
ε
0
E(2A) =
σ
A
⇒
E =
σ
/2
ε
0
= 0.339 N/C
b) If charge
q
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 Summer '08
 Any
 Physics, Vector Space, Electrostatics, Work, Electric charge

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