Question

A wire of resistance 10 ohm is uniformly stretched so that it is 20% longer. Its new resistance will be ……….

Answer 1

as r is directly proportional to length.

r = k × l

here k is resistivity divided by area .

now,

new length = l + 20% of l = l+ 0.2l = 1.2l

so new resistance will be ,

r' = 1.2kl

r' = 1.2(10) = 12 ohm.