NEET Sample Paper NEET Sample Test Paper-65

  • question_answer
    If three wires of same material but different  dimension were used in place of unknown resistance, we get these I-V curve Match the column according to correct curve:
    Wire dimension Corresponding curve
    (p) \[\lambda =1\,\,m\] \[radius=1\,mm\] (i) Curve (1)
    (q) \[\lambda =1\,\,m\] \[radius=2\,mm\] (ii) Curve (2)
    (r) \[\lambda =\frac{1}{2}\,m\] \[radius=\frac{1}{2}\,mm\] (iii) Curve (3)

    A) (p)-(ii); (q)-(iii); (r)-(i)

    B) (p)-(iii); (q)-(ii); (r)-(i)

    C) (p)-(i); (q)-(ii); (r)-(iii)

    D) (p)-(iii); (q)-(ii); (r)-(iii)

    Correct Answer: D

    Solution :

    \[R=\frac{\rho l}{A}\,\,=\,\,\frac{\rho l}{\pi {{r}^{2}}}\] For case \[\left( p \right)\,\,R\,\,\propto \,\,\frac{(1)}{{{(1)}^{2}}}\] For case \[\left( q \right)\,\,R\,\,\propto \,\,\frac{(1)}{{{(2)}^{2}}}\] For case \[\left( r \right)\,\,R\,\,\propto \,\,\frac{(1/2)}{{{(1/2)}^{2}}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,so\,\,{{R}_{r}}>{{R}_{p}}>{{R}_{q}}\] \[and\,\,slope\,\,of\,\,i-v\,cure\,\,=\,\,\frac{i}{v}=\frac{1}{R}\] \[so\,\,slope\,\,r<slope\,\,p<slope\,\,q\] \[\Rightarrow \,\,\,q\,\,\to \,\,line\,(3),\,\,p\to line\,(2),\,\,r\to line\,(3)\]


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