Question

an electric wire is stretched to increase its length by 25% by what percent will the resistance we increase and what will be increased in resistivit​

Answer 1

Answer:

If a copper wire is stretched so that its length increases by 20% then what is the percentage increase in its resistance (assuming its volume remaing constant) ? ∴%Changing in resistance=1.44RoRo×100=0.44×100=44%. JEE Main 2021 conducted by NTA.

Answer 2

Answer:

resistance increased by 20%

resistivity remains the same

Explanation:

r=Rl/a ( r is resistance and R is resistivity )

if lenth is increased by 25% and assuming area of cross section remains intact then

resistance should increase by

r=Rl/a before increase r=R5l/4a after increase

Rl/a×100 = 100×4/5=80%

R5l/4a

since condition 1 is 80% of condition 2 therefore the increase in resistance is 20%

but resistivity is independent of such factors so it remains the same irrespective of length as it only depends on the nature and temperature of the material.