A) 10 cm
B) 20 cm
C) 30 cm
D) 40 cm
Correct Answer: C
Solution :
At neutral point \[\left| \begin{matrix} \,\text{Magnetic field due } \\ \text{to magnet} \\ \end{matrix} \right|=\,\left| \begin{matrix} \text{Magnetic field due } \\ \text{to earth} \\ \end{matrix} \right|\]\[\frac{{{\mu }_{0}}}{4\pi }.\frac{2M}{{{d}^{3}}}=5\times {{10}^{-5}}\Rightarrow {{10}^{-7}}\times \frac{2\times 6.75}{{{d}^{3}}}=5\times {{10}^{-5}}\] \[\Rightarrow d=0.3\ m=30\ cm\]You need to login to perform this action.
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