Find resistance of copper wire.

AI Thread Summary
The resistance of a 1.4 m length of copper wire with a diameter of 5*10^-3 m is calculated using the formula R = p(L/A), where the resistivity of copper is 1.69 * 10^-8. The radius is determined to be 2.5*10^-3 m, leading to an area of approximately 1.96*10^-5 m². Substituting these values into the equation yields a resistance of 1.2*10^-3 Ohm. Initially, the answer was thought to be incorrect, but it was confirmed that the database in the online quiz was faulty. The discussion concludes with relief over resolving the confusion.
Spoonerz
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Homework Statement


Find the resistance of a 1.4 m length of copper wire with diameter of 5*10^-3 m.

Homework Equations


R = p(L/A) where p = resistivity of copper, L = length, A = area

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 said:
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
 
Spoonerz said:
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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