JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank Electric Conduction Ohms and Resistance

  • question_answer
    The length of a given cylindrical wire is increased by 100 %.  Due to the consequent decrease in diameter the change in the resistance of the wire will be                                                         [AIEEE 2003]

    A)            300 %

    B)                                      200 %

    C)            100 %                                      

    D)            50 %

    Correct Answer: A

    Solution :

                 If suppose initial length \[{{l}_{1}}=100\] then \[{{l}_{2}}=100+100=200\] \[\frac{{{R}_{1}}}{{{R}_{2}}}={{\left( \frac{{{l}_{1}}}{{{l}_{2}}} \right)}^{2}}={{\left( \frac{100}{200} \right)}^{2}}\] Þ \[{{R}_{2}}=4{{R}_{1}}\]                    \[\frac{\Delta R}{R}\times 100=\frac{{{R}_{2}}-{{R}_{1}}}{{{R}_{1}}}\times 100=\frac{4{{R}_{1}}-{{R}_{1}}}{{{R}_{1}}}\times 100\]\[=300%.\]


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