If a wire is stretched to double its length, find the new resistance if the original resistance of the wire was R.

Explanation

As we know that `R=(rhol)/A`
in case `R'=(rhol')/A'`
`l'=2l'`
`A'l'=Al` (volume of the wire remains constant)
`A'=A/2rArr` `R'=(rhoxx2l)/(A//2)=4(rhol)/A=4R`