Question

51. Obtain the earth's magnetisation, assuming that the
earth's field can be approximated by a giant bar magnet
of magnetic moment 8.0x1022 Am2. Radius of earth =
6400km.
1) 62.8 Am-1
2) 52.8 Am-1
3) 72.8 Am-
4) 82.8 Am​

Answer 1

Answer:

Option (3) is correct.

Explanation:

The magnetization is that quantity which tells about the magnetic dipole moment of a magnetic material.

It is defined as the magnetic dipole moment of the material per unit volume.

$M = \dfrac mV$.

where,

• $m$ = magnetic dipole moment of the material.

• $V$ = volume of the material.

Given:

• Magnetic moment of the Earth, $m=8.0\times 10^{22}\ Am^2$.

• Radius of earth, $R=6400\ km = 6400\times 10^3\ m$.

The volume of the Earth, $V=\dfrac 43 \pi R^3 = \dfrac 43 \pi \times (6400\times 10^3)^3 = 1.098\times10^{21}\ m^3$.

The Earth's magnetization is given by

$M = \dfrac{8.0\times 10^{22}}{1.098\times 10^{21}}=72.86\ A/m$.

Thus, option (3) is correct.