A short bar magnet is placed in the magnetic meridian of the earth with North Pole pointing north. Neutral points are found at a distance of 30cm from the magnet on the East-West line, drawn through the middle point of

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Quantrex Academy · Accepted Answer

Correct answer: D. 9.7

Horizontal component of earth's magnetic field is along geographical south its North.

\overset{\to}{M} =

Magnetic dipole moment.

A short bar magnet is placed in the magnetic meridian of the earth with North Pole pointing north. Neutral points are

At neutral point on the equatorial line the magnetic field

{B}^{′}

cancels

{B}_{H}

∴ {B}^{′} = {B}_{H}

⇒ \dfrac{{\mu}_{0}}{4\pi}\dfrac{M}{{x}^{3}} = {B}_{H}

⇒ \dfrac{{10}^{- 7} \times M}{{\left(\dfrac{30}{100}\right)}^{3}} = 3.6 \times {10}^{- 5}

⇒ \dfrac{{10}^{- 7} \times {10}^{3} \times M}{27} = 3.6 \times {10}^{- 5}

M = \dfrac{27 \times 3.6 \times {10}^{- 5}}{{10}^{- 4}}

M = 27 \times 3.6 \times {10}^{- 1}

= 9.72

M \approx 9.7

A short bar magnet is placed in the magnetic meridian of the earth...

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