Calculate Resistance of 43m Copper Wire

[shimizua]

Homework Statement

A number 16 copper wire has a diameter of 1.291mm. Calculate the resistance of a 43m long piece of such wire. Use rho=1.72x10-8 Ohm-m for the resistivity of copper. Use units of "ohm".

Homework Equations

R=pl/A
rho is the same thing as the p

The Attempt at a Solution

I just don't know the equation for find A. if you can help me with that then this should be simple since both p and l are given as well as d.

 

[tiny-tim]

Hi shimizua!

A number 16 copper wire has a diameter of 1.291mm.
…
I just don't know the equation for find A.

The question gives the diameter, so you can assume that the cross-section is circular, and use A = πr² (= πd²/4).