Question

a wire of resistance 'p' is pulled to double its length. w what will be it's new resuscitation?

Answer 1

R is directly proportional to l^2

so when the wire is pulled to double its length, resistance will become 2^2 = 4 times

Answer 2

R=ρL/A

When L becomes 2L, A becomes A/2

New R=ρ 2L/A/2

          =4 ρL/A

          =4 R

New resistance becomes 4 times the original one.

But, resistivity remains the same as it is the property of the substance and does not change with length or area.