12th Class Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank MCQ - Current Electricity

  • question_answer
    The figure shows three cylindrical copper conductors along with their face areas and lengths. Rank them according to the current through them, greatest first when the same potential difference V is placed across their lengths.

    A) \[{{i}_{l}}={{i}_{ll}}={{i}_{lll}}\]                  

    B) \[{{i}_{l}}>{{i}_{ll}}>{{i}_{lll}}\]

    C) \[{{i}_{l}}<{{i}_{ll}}<{{i}_{lll}}\]                  

    D) \[({{i}_{l}}={{i}_{lll}})<{{i}_{ll}}\]

    Correct Answer: D

    Solution :

    (d) \[({{i}_{l}}={{i}_{lll}})<{{i}_{ll}}\] We know that, \[R=\rho \frac{l}{A}\] \[\therefore {{R}_{l}}=\rho \frac{L}{A}\]                                                                                                            …(1)             \[{{R}_{ll}}='\rho \frac{1.5L}{A/2}=3\rho \frac{L}{A}\]                                                                                                 ….(2)             \[{{R}_{lll}}=\rho \frac{L/2}{A/2}=\rho \frac{L}{A}\]                                                                                                     …(3) Using eqs. (1), (2) and (3), we can say that             \[{{R}_{ll}}>({{R}_{l}}={{R}_{lll}})\] \[\therefore ({{i}_{l}}={{i}_{lll}})<{{i}_{ll}}\] From Ohm's Law, we know that V = IR when same potential difference is applied \[l\propto \frac{l}{R}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner