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

  • question_answer There are two electric bulbs of 40 W and 100 W. Which one will be brighter when first connected in series and then in parallel,                                                      [MP PET 1993]

    A)            40 W in series and 100 W in parallel

    B)            100 W in series and 40 W in parallel

    C)            40 W both in series and parallel will be uniform

    D)            100 W both in series and parallel will be uniform

    Correct Answer: A

    Solution :

               \[\frac{{{R}_{1}}}{{{R}_{2}}}=\frac{{{P}_{2}}}{{{P}_{1}}}=\frac{100}{40}=\frac{5}{2}\]. Resistance of 40 W bulb is \[\frac{5}{2}\] times than 100 W. In series, \[P={{i}^{2}}R\] and in parallel, \[P=\frac{{{V}^{2}}}{R}\]. So 40 W in series and 100 W in parallel will glow brighter.

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