# Find resistance of copper wire.

## 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?

## Answers and Replies

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
Mentor
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.