A) \[4\times {{10}^{-8}}\text{tesla}\]
B) \[3.5\times {{10}^{-8}}\text{tesla}\]
C) \[5\times {{10}^{-8}}\text{tesla}\]
D) \[3\times {{10}^{-8}}\text{tesla}\]
Correct Answer: C
Solution :
| [c] Along the equatorial line, magnetic field strength\[B=\frac{{{\mu }_{0}}}{4\pi }\frac{M}{{{\left( {{r}^{2}}+{{\ell }^{2}} \right)}^{3/2}}}\] |
| Given: \[M=4J{{T}^{-1}}\] |
| \[r=200cm=2m\] |
| \[\ell =\frac{6cm}{2}=3cm=3\times {{10}^{-2}}m\] |
| \[\therefore \]\[B=\frac{4\pi \times {{10}^{-7}}}{4\pi }\times \frac{4}{{{\left[ {{2}^{2}}+{{\left( 3\times {{10}^{-2}} \right)}^{2}} \right]}^{{\scriptstyle{}^{3}/{}_{2}}}}}\] |
| Solving we get, \[B=5\times {{10}^{-8}}\]tesla |
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