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NEET Sample Paper NEET Sample Test Paper-66

  • question_answer
    A constant current i is passed through a resistor. Taking the temperature coefficient of resistance into account, indicate which of the plots shown in figure best represents the rate of production of thermal energy in the resistor  

    A) a                                 

    B) b

    C) c                                  

    D) d

    Correct Answer: D

    Solution :

    Thermal energy in resistor is \[U={{t}^{2}}Rt\] where \[R={{R}_{0}}(1+\alpha t)\] \[\Rightarrow \,\,\,U={{i}^{2}}{{R}_{0}}\left( 1+\alpha t \right)t={{i}^{2}}{{R}_{0}}t+{{i}^{2}}{{R}_{0}}{{t}^{2}}\] So \[\frac{dU}{dt}\,=\,\,{{i}^{2}}{{R}_{0}}(1+\alpha t)\] With the time temperature increases, hence \[dU/dt\] increases. This is best shown by curve (d).


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