NEET-XII-Physics
36: Permanent Magnets
- #11The magnetic moment of the assumed dipole at the earth’s centre is 8.0 × 1022 A m2. Calculate the magnetic field B at the geomagnetic poles of the earth. Radius of the earth is 6400 km.Ans : Given:
Magnetic moment of dipole at Earth's centre, M = 8.0 × 1022 Am2
Radius of Earth, d = 6400 km
The geomagnetic pole is at the end of the position (axial) of Earth.
Thus, the magnetic field at the axial point of the dipole `` \left(B\right)`` is given by
`` B=\frac{{\,\mathrm{\,\mu \,}}_{0}}{4\,\mathrm{\,\pi \,}}\frac{\mathit{2}M}{{d}^{\mathit{3}}}``
`` \Rightarrow B=\frac{{10}^{-7}\times 2\times 8\times {10}^{22}}{{\left(64\right)}^{3}\times {10}^{15}}``
`` \Rightarrow B=6\times {10}^{-5}\,\mathrm{\,T\,}=60\,\mathrm{\,\mu T\,}``
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