Question

The resistance of wire is 20ohm. Find the resistance of the wire when it is stretched so that the length increases by 10%. (please explain it in detail with ans)

Answer 1

The wire’s length is stretched to twice its length I.e. area of cross section decreases or becomes half, since volume remains the same.

R= (row*L)/A

row - specific resistance

L - length of wire

A- Area of cross section wire

Ur condition

New R= (row*2L)/(new A)

new A = old A/2 as per below derivation

Hence new R = (row*2L)/(A/2)

New R = 4*( (row*L)/A))=4*old R

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For area and length relation

Volume of cylinder =pi*r*r*L=A*L

r - radius of flat surface or tip of wire.

A=area of cross section

A=pi*r*r

I hope this helps!

Feel free to correct the mistakes :)