Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    A winding wire which is used to frame a solenoid can bear a maximum 10 A current. If length of solenoid is 80 cm and its cross-sectional radius is 3 cm then required length of winding wire is (B = 0.2 T)

    A)  \[1.2\times {{10}^{2}}m\]                           

    B)  \[4.8\times {{10}^{2}}m\]

    C)  \[2.4\times {{10}^{3}}m\]                           

    D)  \[6\times {{10}^{3}}m\]

    Correct Answer: C

    Solution :

                    \[B=\frac{{{\mu }_{0}}Ni}{l}\]; where N = total number of turns, \[l=\] length of the solenoid \[\Rightarrow \]               \[0.2=\frac{4\pi \times {{10}^{-7}}\times N\times 10}{0.8}\] \[\Rightarrow \]               \[N=\frac{4\times {{10}^{4}}}{\pi }\] Since N turns are made from the winding wire so length of the wire \[(L)=2\pi r\times N\][\[2\pi r\]= length of each turns] \[\Rightarrow \]               \[L=2\pi \times 3\times {{10}^{-2}}\times \frac{4\times {{10}^{4}}}{\pi }\]                 \[=2.4\times {{10}^{3}}m\]


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