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

  • question_answer An electric kettle has two heating coils. When one coil is used, water in the kettle boils in 5 minutes, while when second coil is used, same water boils in 10 minutes. If the two coils, connected in parallel are used simultaneously, the same water will boil in time                                                [MP PET 2001]

    A)            3 min 20 sec                          

    B)            5 min

    C)            7 min 30 sec                          

    D)            2 min 30 sec

    Correct Answer: A

    Solution :

                       In parallel  \[\frac{1}{{{t}_{p}}}=\frac{1}{{{t}_{1}}}+\frac{1}{{{t}_{2}}}\] Þ \[{{t}_{p}}=\frac{{{t}_{1}}{{t}_{2}}}{{{t}_{1}}+{{t}_{2}}}\]                    \[=\frac{5\times 10}{5+10}=\frac{50}{15}=3.33\,\min \]\[=3\,min.\,20\,sec\]

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