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  • Help me answer: A copper wire is stretched to make it 0.5 % longer. The percentage change in its electrical resistance if its volume remains unchanged is :

A copper wire is stretched to make it 0.5 % longer. The percentage change in its electrical resistance if its volume remains unchanged is :

  • Option 1)

    2.0 %

  • Option 2)

    2.5 %

  • Option 3)

    1.0 %

  • Option 4)

    0.5 %

Answers (1)

best_answer

 

Resistivity -

R=\rho\frac{l}{A}

- wherein

\rho\rightarrow  resistivity / specific resistance

 

Volume is constant

Let initially area of wire is A, length is L and resistance be R

\therefore V = A.l \ and \ R = \frac{\rho l }{A}

A.l = A1 ( l + 0.005l )

A_{1} = \frac{A}{1.005}

R_{1} = \frac{\rho (1.005)l}{\frac{A}{1.005}} = R (1.005)^{2}=1.01R

percentage change=\frac{ (1.01-1)l}{1}\times100=1%

 

 

 


Option 1)

2.0 %

Option 2)

2.5 %

Option 3)

1.0 %

Option 4)

0.5 %

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