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Class 12
Physics
Magnetism and Matter
a short bar magnet placed in a horizontal plane ha...

Question:
A short bar magnet placed in a horizontal plane has its axis alignedalong the magnetic north-south direction. Null points are found on the axis of the magnet at 14 cm from the centre of the magnet. The earth's magnetic field at the place is 0.36 G and the angle of dip is zero. What is the total magnetic field on the normal bisector of the magnet at the same distance as the null-point (i.e., 14 cm) from the centre of the magnet? (At null points, field due to a magnet is equal and opposite to the horizontal component of earth's magnetic field.)

Answer:

Earth's magnetic field at the given place, H= 0.36 G

The magnetic field at a distance d, on the axis of the magnet is given as:

Where, μ₀= Permeability of free space

M= Magnetic moment

The magnetic field at the same distance d, on the equatorial line of the magnet is given as:

Total magnetic field, B = B₁+ B₂

Hence, the magnetic field is 0.54 G in the direction of earth's magnetic field.

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