(B) When a magnet is placed with its south pole pointing towards the geographic north,the null points are located on the axial line of the magnet.For

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(B) When a magnet is placed with its south pole pointing towards the geographic north,the null points are located on the axial line of the magnet.For a short magnet,the magnetic field $B$ on its axial line at a distance $d$ from its center is given by $B = \frac{2M}{d^3}$,where $M$ is the magnetic moment.At the null point,the magnetic field of the magnet is equal and opposite to the horizontal component of the Earth's magnetic field $(B_H)$.Given: $d = 20 \, cm$,$B_H = 0.3 \, gauss$.Equating the fields: $\frac{2M}{d^3} = B_H$.Substituting the values: $\frac{2M}{(20)^3} = 0.3$.$\frac{2M}{8000} = 0.3$.$2M = 0.3 \times 8000 = 2400$.$M = 1200 \, e.m.u. = 1.2 \times 10^3 \, e.m.u.$

Class 12 Physics Magnetism and Matter Magnetic Equipment's (Tangent galvanometer, Vibration magnetometer and Neutral point)

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$A$ very small magnet is placed in the magnetic meridian with its south pole pointing north. The null point is obtained $20 \, cm$ away from the centre of the magnet. If the earth's magnetic field (horizontal component) at this point is $0.3 \, gauss$,the magnetic moment of the magnet is:

A
$8.0 \times 10^2 \, e.m.u.$
B
$1.2 \times 10^3 \, e.m.u.$
C
$2.4 \times 10^3 \, e.m.u.$
D
$3.6 \times 10^3 \, e.m.u.$

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Magnetism and Matter

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Magnetic Equipment's (Tangent galvanometer, Vibration magnetometer and Neutral point)

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$A$ very small magnet is placed in the magnetic meridian with its south pole pointing north. The null point is obtained $20 \, cm$ away from the centre of the magnet. If the earth's magnetic field (horizontal component) at this point is $0.3 \, gauss$,the magnetic moment of the magnet is:

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The time period of a thin bar magnet in Earth's magnetic field is $T$. If the magnet is cut into two equal parts perpendicular to its length,the time period of each part in the same field will be

$A$ magnet makes $20$ and $15$ oscillations in $1$ minute at two places where the angles of dip are $30^{\circ}$ and $60^{\circ}$ respectively. What is the ratio of the total magnetic fields at these two places?

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