10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    Two bulbs A and Bare rated 100 W, 120V and 10 W, 120 V respectively. They are connected in parallel across a 120 V source. Find the current passing through each bulb and the bulb which consumes more energy?

    A) 0.83 A, Bulb B  

    B) 0.083 A, Bulb A                

    C) 0.83 A, Bulb A  

    D) 0.083 A, Bulb B

    Correct Answer: C

    Solution :

    Resistance of bulb A is \[{{R}_{1}}=\frac{{{V}^{2}}}{{{P}_{1}}}=\frac{{{(120)}^{2}}}{100}=144\,\Omega \] Resistance of bulb B is \[{{R}_{2}}=\frac{{{V}^{2}}}{{{P}_{2}}}=\frac{{{(120)}^{2}}}{10}=1440\,\Omega \] As the bulbs are connected in parallel to the source, the voltage across each bulb is the same. l in bulb A is \[{{i}_{1}}=\frac{V}{{{R}_{1}}}=\frac{120}{144}=0.83A\] I in bulb B is \[{{i}_{2}}=\frac{V}{{{R}_{2}}}=\frac{120}{1440}=0.083A\] Power consumed by bulb A is 100 W and by bulb B is 10 W. Bulb A consumes more energy than bulb B.


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