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J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    A railway compartment is lit up by thirteen  lamps each taking \[2.1\text{ }A\]at\[15\text{ }V\]. The heat   generated per second in each lamp will be m

    A)  \[4.35\text{ }cal\]      

    B)  \[5.73\text{ }cal\]             

    C)  \[7.5\text{ }cal\]        

    D)  \[2.5\text{ }cal\]              

    Correct Answer: C

    Solution :

    From Joule's law, for a current carrying conductor at a definite temperature the rate of production of heat is given by \[H=Vit\] where i is current, V the potential difference and t the time. Given, \[V=15\text{ }volt,\] \[i=2.1A,\] \[t=1s\] \[\therefore \] \[H=15\times 2.1\times 1=31.5J\] Also,     \[1cal=4.2J\] \[\therefore \] \[H=\frac{31.5}{4.2}=7.5\,cal\]


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