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PHYSICS 241E - Quiz No. 2 - Section 5
October 21, 1996

Two spherical Gaussian surfaces are drawn symmetrically around two concentric conducting shells of radii R tex2html_wrap_inline184 and R tex2html_wrap_inline186 as shown in the figure.

figure221

S tex2html_wrap_inline184 encloses electrix flux of -Q/ tex2html_wrap_inline190

S tex2html_wrap_inline186 encloses electrix flux of +Q/ tex2html_wrap_inline190

Gauss' Law states that tex2html_wrap_inline196

(1) Charges on R tex2html_wrap_inline184 -shell and R tex2html_wrap_inline186 -shell are equal to

eqnarray21

(2) Magnitude of electric field at r>R tex2html_wrap_inline186 is

eqnarray43

(3) Work done in bringing charge q tex2html_wrap_inline206 from tex2html_wrap_inline208 to r=R tex2html_wrap_inline186 is

eqnarray73

(4) Electrical potential difference tex2html_wrap_inline212 between R tex2html_wrap_inline184 and R tex2html_wrap_inline186 is

eqnarray103

(5) The space between the conducting shells is filled with a substance of dielectric constant tex2html_wrap_inline218 . If the shells have equal and opposite charges Q and -Q, what is the capacitance?

eqnarray135


Blaine E. Norum
Mon Oct 21 15:14:23 EDT 1996