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10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    Three bulbs \[{{B}_{1}},{{B}_{2}}\] and \[{{B}_{3}}\] are connected to the mains as shown in the figure. How will the incandesence of the bulb  \[{{B}_{1}}\]be affected, if one of the bulb \[{{B}_{2}}\]or \[{{B}_{3}}\] is disconnected from the circuit

    A)  No change in the incandescence

    B)  Bulb \[{{B}_{1}}\] will become brighter

    C)  The bulb \[{{B}_{1}}\] will become less brighter  

    D)  The bulb \[{{B}_{1}}\] may become brighter or dimmer depending upon the candle power of the bulb which is disconnected

    Correct Answer: C

    Solution :

     Let the total current supplied by the battery in the given circuit be I. In that case, current in bulb \[{{B}_{1}}\] is I and in each of the bulbs\[{{B}_{2}}\]or\[{{B}_{3}}\]is\[\frac{I}{2}\]. When one resistance is removed from parallel, \[{{R}_{eq}}\]increases. The current supplied decreases, say it becomes\[I'\].This is also the current that now flows into \[{{B}_{2}}\](\[{{B}_{3}}\] having been removed). \[I'\]less than\[I\]but greater than\[\frac{I}{2}\]. So, the current through \[{{B}_{1}}\] decreases while that through\[{{B}_{1}}\]decreases.


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