Calculate the resistance of an aluminium wire of length 50 cm and cross sectional area `2.0mm^(2)`. The resistivity of aluminium is `(rho)=2.6xx10^(-8)(Omega)m.`

Explanation

The resistance is R=(rho)(l)/(A)`
`=((2.6xx10^(-8)(Omega)m)xx(0.50m))/(2xx10^(-6) m^(2))=0.0065(Omega).`
We aarived at Ohm's law by making several assumption about the existence and behaviour of the free electrons. These assumptions are mot valid for semiconductors, insulators, solutions, ets. Ohm's law cannat be applied in such cases.