A wire has a resistance `R`. What wil will be its resistance if it is stretched to double its length?

Explanation

Let `V` be the volume of wire then
`V=Al`
`:. A=V/l`
Substituting this `i` `R=rho1/A,` we have `R=rhol^2/V`
So, for given volume and material (i.e. `V` and rho are constant)
`R propl^2`
when `l` is doubled resistance will become four times or the new resistance will be `4 R`.