P27_050.PDF

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Chapter 27 - 27.50
50. (a) We denote the copper wire with subscript c and the aluminum wire with subscript a .
A = (2 . 75
×
10 8
·
m)(1 . 3m)
=1 . 3
×
10 3 .
(5 . 2
×
10 3 m) 2
(b) Let R = ρ c L/ ( πd 2 / 4) and solve for the diameter d of the copper wire:
d = 4 ρ c L
4(1 . 69
×
10 8
·
m)(1 . 3m)
=4 . 6
×
10 3 m .
π (1 . 3
×
10 3 Ω)
R = ρ a L
πR =
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