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JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank Self Evaluation Test - Current Electricity

  • question_answer
    A hank of uninsulated wire consisting of seven and a half turns is stretched between two nails hammered into a board to which the ends of the wire are fixed. The resistance of the circuit between the nails is determined with the help of electrical measuring instruments. Determine the proportion in which the resistance will change if the wire is unwound so that the ends remain to be fixed to the nails.

    A) 225

    B) 15

    C) 240

    D) 250

    Correct Answer: A

    Solution :

    [a] Let the resistance of half the turn be R. Then in the former case, we have fifteen resistors of resistance R connected in parallel, the total resistance being R/15. In the latter case, we have the same fifteen resistors connected in series, the total resistance being 15R. Therefore, as a result of unwinding, the resistance of the wire will increase by a factor of 225.


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