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NEET Sample Paper NEET Sample Test Paper-13

  • question_answer
    Copper of fixed volume V is drawn into wire of length \[l.\] When this wire is subjected to a constant force F, the extension produced in the wire is \[\Delta l.\]Which of the following graphs is a straight line?

    A) \[\Delta l\] versus\[\frac{1}{l}\]   

    B)  \[\Delta l\]versus \[{{l}^{2}}\]

    C) \[\Delta l\]versus\[\frac{1}{{{l}^{2}}}\]             

    D)  \[\Delta l\]versus \[l\]

    Correct Answer: B

    Solution :

     Young's modulus \[Y=\frac{Stress}{Strain}\] or \[Y=\frac{F/A}{\Delta l/l}=\frac{Fl}{A\Delta l}\] \[\Rightarrow \]\[\Delta l=\frac{Fl}{AY}\]                                      (i) The volume of wire V= Al or         \[A=\frac{V}{l}\]                                               (ii) Substituting the value of A from (ii) in equation (i) We get \[\Delta l=\frac{F{{l}^{2}}}{VY}\Rightarrow \Delta l\propto {{l}^{2}}\] Hence the graph of \[\Delta l\]versus\[{{l}^{2}}\]will give a straight line.


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