Question

Resistance of a given wire of length l is 3 ohm. The wire is stretch uniformly such that its length becomes 2L. find the new resistance of the stretched wire.

Answer 1

Answer:

12 ohms

Explanation:

Given,

R=3

R = Pxl/A or 3 =Pxl/A

Now, Resistance of Stretched Wire:

R = Px2l/A/2

R = 4x(Pxl/A) (putting : Pxl/A = 3)

R = 4x3

R = 12 ohms

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Answer 2

Answer:

New resistance is 6ohm.

Explanation:

let, the first resistance be R1

     the second resistance be R2

Here, R1= 3ohm

         length = l

area of cross section be A

now, R1= P l/A      

       3 = Pl/A       ---------1

when length is double

     R2 = P2l/A    ----------2

equation 1 divided 2

3/R2 = Pl/A*A/P2l

3/R2 = 1/2

  R2 = 6 ohm

therefore, the first resistance be R1 .