A copper rod of length 20cm and cross-sectional area `2mm^(2)`is joined with a similar aluminium rod as shown in figure .Find the resistance of the combination between the ends, Resistivity of copper `=1.7xx10^(-8)(Omega)m`and that of aluminium`=2.6xx10^(-8)(Omega)m`.

Explanation

The resistance of the copper rod
`(rho)(l)/(A)=((1.7xx10^(-8)(Omega)m)xx(20xx10^(-2)m))/(2.0xx10^(-6)m^(2)`
`=1.7xx10^(-3)(Omega)`.
Similarly, the resistance of the aluminium rid `=2.6xx10^(-3)(Omega).`
these rods are joined in parallel so that the equivalent risistance R between the ends is given by
`1/R=1/(1.7xx10^(-3)(Omega))+1/(2.6xx10^(-3)(Omega))`.
or, `R=(1.7xx2.6)/(4.3)xx10^(-3)(Omega)~~1.0m(Omega).