JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर JEE PYQ-Current Electricity Charging and Discharging of Capacitors

  • question_answer
    A piece of copper and another of germanium are cooled from room temperature to 77 K, the resistance of                                 [AIEEE 2004]

    A) each of them increases

    B) each of them decreases

    C) copper decreases and germanium increases

    D) copper increases and germanium decreases

    Correct Answer: C

    Solution :

    [c] We know that resistance of conductor is directly proportional to temperature\[(i.e.,R\propto \Delta t)\] while resistance of semiconductor is inversely proportional to temperature\[\left( i.e.,R\propto \frac{1}{\Delta t} \right)\].
    Therefore, it is clear that resistance of conductor decreases with decrease in temperature or vice-versa, while in case of semiconductor, resistance increases with decrease in temperature and vice-versa.
    Since, copper is pure conductor and germanium is a semiconductor hence, due to decrease in temperature, resistance of conductor decreases while that of semiconductor increases.


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