CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2005

  • question_answer
    Three long, straight parallel wires, carrying current, are arranged as shown in figure. The  force experienced by a 25 cm length of wire C is:

    A)  \[{{10}^{-3}}N\]                              

    B)  \[2.5\times {{10}^{-3}}N\]

    C)  zero                                     

    D)  \[1.5\times {{10}^{-3}}N\]

    Correct Answer: C

    Solution :

    Force on wire C due to wire D.                 \[{{F}_{1}}=\frac{{{\mu }_{0}}}{2\pi }\,\,\frac{{{I}_{1}}{{I}_{2}}}{r}l\]                        (repulsive)                                 \[=2\times {{10}^{-7}}\times \frac{30\times 10}{3\times {{10}^{-2}}}\times 25\times {{10}^{-2}}\]                                 \[=2\times {{10}^{-7}}\times 2500\]                                 \[=5\times {{10}^{-4}}N\] Force on wire C due to wire G                 \[{{F}_{2}}=\frac{{{\mu }_{0}}}{2\pi }\,\frac{{{I}_{1}}{{I}_{2}}}{r}l\]                            (repulsive)                 \[=\frac{2\times {{10}^{-7}}\times 10\times 20}{2\times {{10}^{-2}}}\times 25\times {{10}^{-2}}\]                 \[=2\times {{10}^{-7}}\times 2500\]                 \[=5\times {{10}^{-4}}N\] Net force \[={{F}_{1}}-{{F}_{2}}\]                 \[=5\times {{10}^{-4}}N-5\times {{10}^{-4}}N\]                 \[=0\]


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