Question

what would happen to resistance of a wire if it is stretched to double its length justify your answer

Answer 1

resistance is double because resistance is directly proportional to length of wire

Answer 2

resistance will become 1/4 as
$\frac{r1}{r2} = { \frac{l1}{l2 } }^{2} \\ l2 = 2 \times l \\ l1 = l \\ \frac{r1}{r2} = { \frac{1}{2} }^{2} \\ \frac{r1}{r2} = \frac{1}{4} \\ r2 = 4times$