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

  • question_answer The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use                                      [AIEEE 2005]

    A)            \[400\,\Omega \]               

    B)            \[200\,\Omega \]

    C)            \[40\text{ }\Omega \]      

    D)            \[20\,\Omega \]

    Correct Answer: C

    Solution :

                       It is given \[{{R}_{Hot}}=10\,{{R}_{Cold}}\] also resistance at rated temperature \[R=\frac{{{V}^{2}}}{P}=\frac{200\times 200}{100}=400\,\Omega \]. So resistance when lamp not in use. \[{{R}_{Cold}}=\text{ }\frac{{{R}_{Hot}}}{10}=\frac{400}{10}=40\,\Omega \]

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