Question

a wire is stretched so that its length becomes 6/5 times its original length. If its original resistance is 25 ohm find its new resistance and resistivity

Answer 1

R=¶ l/a = ¶ l×l/v 25ohm = ¶l×l/v L =6/5 l R' = ¶ L×L/ v  = ¶( 6 /5 l × 6/5 l)/v = 36/25 (¶l×l/v) = 36/25×25 ohm =36 ohm Resistivity of a substance doesn't depend on length *L - new length   l - original length   R' - new resistance   R- original resistance   ¶ -resistivity  

Answer 2

R is directly proportional to L
so as length increases by 6/5
then R also increases by 6/5
25×6/5 = 30
R = 30 ohm