P27_058.PDF

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Chapter 27 - 27.58
58. (a) Since ρ = RA/L = πRd 2 / 4 L = π (1 . 09
×
10 3 Ω)(5 . 50
×
10 3 m) 2 / [4(1 . 60 m)] = 1 . 62
×
10 8
·
m,
the material is silver.
(b) The resistance of the round disk is
A = 4 ρL
πd 2 = 4(1 . 62
×
10 8
·
m)(1 . 00
×
10 3 m)
=5 . 16
×
10 8 .
π (2 . 00
×
10 2 m) 2
R = ρ L
 
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