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
    The masses of the three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistance is

    A) 1 : 3 : 5

    B) 5 : 3 : 1

    C) 1 : 25 : 125

    D) 125 : 45 : 3

    Correct Answer: D

    Solution :

    [d] \[R=\frac{\rho l}{\pi {{r}^{2}}}.\]But \[m=\pi {{r}^{2}}ld\text{   }\therefore \pi {{r}^{2}}=\frac{m}{ld}\] \[\therefore {{R}_{1}}=\frac{pl_{1}^{2}d}{{{m}_{1}}},{{R}_{2}}=\frac{pl_{2}^{2}d}{{{m}_{2}}};{{R}_{3}}=\frac{pl_{3}^{2}d}{{{m}_{3}}}\] \[{{R}_{1}}:{{R}_{2}}:{{R}_{3}}=\frac{l_{1}^{2}}{{{m}_{1}}}:\frac{l_{2}^{2}}{{{m}_{2}}}:\frac{l_{3}^{2}}{{{m}_{3}}}=125:45:3\]


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