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JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Evening)

  • question_answer
    Two rods A and B of identical dimensions are at temperature \[30{}^\circ C\]. If A is heated upto \[180{}^\circ C\]and B upto \[T{}^\circ C\], then the new lengths are the same. If the ratio of the coefficients of linear expansion of A and B is \[4:3\], then the value of T is [JEE  Main Online Paper (Held on 11-jan-2019 Evening)]

    A) \[200{}^\circ C\]                                  

    B) \[270{}^\circ C\]

    C) \[230{}^\circ C\]                      

    D)   \[250{}^\circ C\]

    Correct Answer: C

    Solution :

    \[\Delta {{l}_{A}}=\Delta {{l}_{B}}\] \[{{l}_{OA}}{{\alpha }_{A}}{{(\Delta T)}_{A}}={{l}_{OB}}{{\alpha }_{B}}{{(\Delta T)}_{B}}\] \[\frac{\Delta T{{)}_{A}}}{{{(\Delta T)}_{B}}}=\frac{{{l}_{OB}}}{{{l}_{OA}}}\times \frac{{{\alpha }_{B}}}{{{\alpha }_{A}}}\] \[\frac{180-30}{T-30}=1\times \frac{3}{4}\] \[3T-90=600;T={{230}^{o}}C\]


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