JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors Question Bank Heating Effect of Current

  • question_answer A coil develops heat of 800 cal/sec. When 20 volts is applied across its ends. The resistance of the coil is (1 cal = 4.2 joule)                                                          [MP PET 1994]

    A)            \[1.2\,\Omega \]                

    B)            \[1.4\,\Omega \]

    C)            \[0.12\,\Omega \]             

    D)            \[0.14\,\Omega \]

    Correct Answer: C

    Solution :

                       \[H=\frac{{{V}^{2}}t}{4.2\,R}\] or  \[\frac{H}{t}=\frac{{{V}^{2}}}{4.2\,R}\]            Þ \[800=\frac{20\times 20}{4.2\times R}\]Þ \[R=\frac{5}{42}=0.119\approx 0.12\,\Omega \]


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