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

  • question_answer If two bulbs of wattage 25 and 100 respectively each rated at 220 volt are connected in series with the supply of 440 volt, then which bulbs will fuse                                [MNR 1988]

    A)            100 watt bulb                      

    B)            25 watt bulb

    C)            None of them                     

    D)            Both of them

    Correct Answer: B

    Solution :

                       Resistance of 25 W bulb \[=\frac{220\times 220}{25}=1936\,\Omega \] Its safe current \[=\frac{220}{1936}=0.11\,\,amp.\] Resistance of 100 W bulb \[=\frac{220\times 220}{100}=484\,\Omega \] Its safe current \[=\frac{220}{484}=0.48\,\,amp.\] When connected in series to 440 V supply, then the current \[I=\frac{440}{(1936+484)}=0.18\,amp.\] Thus current is greater for 25 W bulb, so it will fuse.


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