Question

a wre is stretched 30% what is the percentage change in its resistance

Answer 1

if initial length of the wire =L
final length (L')=L+L.30/100=13L/10
as the wire was stretched the area of the wire will decrease
if A is the initial area then the final area is=A'
now volume will remain same
then. L.A=L'.A'
then A'=10A/13
now initial resistance =R=&L/A
final resistance =R'=&L'/A'=&13L/10/10A/13
R'=169/100R
Percentage change in resistance =(R'-R)100%
=69%
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