A lump of copper of mass 10 g and of density `9g.cm^-3` is given, what should be the length and cross section of the wire made from it so that its resistance is 2 ohm. (Given ,specific resistance of copper `1.8 times 10^-6 Omega cm`).

Explanation

Now, by multiplying (1) and (2) we get ,
`l^2=10/9times10/9times10^6`or,`l=10/9times10^3cm=11.1m`
Again dividing (1) by (2) we get, `A^2=10^-6`
or, `A=10^-3cm^2=10^-1mm^2=0.1mn^2`