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## Homework Statement

A 10-g piece of copper is to be formed into a wire of radius 1.0 mm at a temperature of 50°

C. What is the resistance of this wire? (Hint: you will need to look up the density of copper.) If a potential of 12 V is put across this wire, what is the drift velocity?

## Homework Equations

J=I/A=nqv

_{d}

R=ρ(L/A)

ρ=ρ

_{0}(1+[itex]\alpha[/itex](T-T

_{0})

ρ

_{0}=1.7*10^-8 at 20°C

## The Attempt at a Solution

The resistivity of copper at 50°C is:

ρ=ρ

_{0}(1+[itex]\alpha[/itex](T-20) where [itex]\alpha[/itex]=3.9*10^-3 1/°C

Substituting values, ρ=1.899*10^-8 Ωm

I hit a brick wall here, though. I don't know how to get from density of copper to length of the wire for R=ρ(L/A)

Any advice?