If a Cu wire is stretched to make it 0.1% longer , the %age change in its resistance is ?

When stretched, the volume remains constant. So, A1l1=A2l2 Original resistance R1= rl1/A1 Final Resistance R2= rl2/A2 Percentage change in resistance = (R2-R1)x100/(R1) Substitute the values and try to get the answer