Question

If a copper wire is stretched by one tenth of its original length then change in resistance is

Answer 1

R = ρL/A

Original is L * A

Original Volume = LA

Stretch wire Length = L + (L/10) = 11L/10

Stretched wire Area  = LA / (11L/10) = 10A/11

Stretched wire resistance = ρ(11L/10)/(10A/11)

= ρ(L/A)(11*11)/(10*10)

ρ(L/A)*121/100

= R*121/100

Change = R*121/100 - R = 21R/100

% Change = {(21R/100)/R}*100 = 21 %

21 % Increase in Resistance