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Find resistance of copper wire.

by Spoonerz
Tags: area, length, ohm, resistance, resistor
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Spoonerz
#1
Sep13-10, 08:32 PM
P: 5
1. The problem statement, all variables and given/known data
Find the resistance of a 1.4 m length of copper wire with diameter of 5*10^-3 m.


2. Relevant equations
R = p(L/A) where p = resistivity of copper, L = length, A = area


3. The attempt at a solution
The resistivity of copper is (1.69 * 10^-8). Radius is d/2 (5*10^-3) / (2) = (2.5*10^-3)
With the radius, the Area A = pi(2.5*10^-3)^2 = (1.96*10^-5).

Plugging it into the equation R = p(L/A)
(1.69*10^-8)*(1.4) / (1.96*10^-5) = (1.2*10^-3) Ohm

There were two similar questions like this where the same approach yield me the correct answer. Somehow this answer I get is incorrect. What am I doing wrong?

On a side note, how many questions may I post?
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Spoonerz
#2
Sep15-10, 01:05 PM
P: 5
Quote Quote by Spoonerz View Post
Plugging it into the equation R = p(L/A)
(1.69*10^-8)*(1.4) / (1.96*10^-5) = (1.2*10^-3) Ohm
1.2*10^-3 Ohm is the correct answer after all. It was just the faulty database in the online quiz. =D
berkeman
#3
Sep15-10, 01:12 PM
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berkeman's Avatar
P: 41,320
Quote Quote by Spoonerz View Post
1.2*10^-3 Ohm is the correct answer after all. It was just the faulty database in the online quiz. =D
Ouch, that hurts! Glad you got it sorted out.


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