NEET Sample Paper NEET Sample Test Paper-17

  • question_answer
    A long wire bent as shown in the figure carries I. If the radius of the semi-circular portion is a, the magnetic field at the centre of the semi-circle is:

    A) \[\frac{{{\mu }_{0}}I}{4a}\]                        

    B) \[\frac{{{\mu }_{0}}I}{4\pi a}\sqrt{{{\pi }^{2}}+4}\]    

    C)   \[\frac{{{\mu }_{0}}I}{4a}+\frac{{{\mu }_{0}}I}{2\pi a}\]                    

    D)  \[\frac{{{\mu }_{0}}I}{4\pi a}\sqrt{{{\pi }^{2}}-4}\]

    Correct Answer: B

    Solution :

    \[{{B}_{1}}=\frac{{{\mu }_{0}}}{4\pi }\times \frac{2\pi I}{a}\times \frac{1}{2}\](due to semicircular part)\[{{B}_{2}}=\frac{{{\mu }_{0}}}{4\pi }\times \frac{2I}{a}\](due to parallel parts of currents) These two fields are at right angles to each other. Hence, resultant field \[B=\sqrt{B_{i}^{2}+B_{2}^{2}}=\frac{{{\mu }_{0}}I}{4\pi a}\sqrt{{{\pi }^{2}}+4}\] Hence, the correction option is [b].


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