27. Resistors & DC Circuits

A copper wire with a radius of $2.0\mathrm{ mm}$ and a length of $0.80\mathrm{ m}$ is connected across the terminals of a $9.0\mathrm{V}$ battery. How much current flows in the wire?

A copper wire and an aluminum wire have the same diameter. If the copper wire is $10\mathrm{ m}$long, how long is the aluminum wire if they have the same resistance?