Answer the question regarding earth's magnetism:
The earth's field, it is claimed, roughly approximates the field due to a dipole of magnetic moment `8 xx 10^(22) JT^(-1)` located at its centre. Check the order of magnitude of this number in some way.

Answer the following questions regarding earth's magnetism If a map of magnetic field lines is prepared at Melbourne in Australia , would the lines seem to go into the ground or come out of the ground .

A magnetised needle of magnetic moment 4.8xx10^(-2)JT^(-1) is placed at 30^@ with the direction of uniform magnetic field of magnitude 3xx10^(-2)T . Calculate the torque acting on the needle.

A wheel with 8 metallic spokes each 50 cm long is rotated with a speed of 120 rev. "min"^(-1) in a plane normal to the horizontal component of the Earth's magnetic field. The Earth's magnetic field at the place in 0.4 G and the angle of dip is 60^(@) . Calculate the emf induced between the axle and the rim of the wheel. How will the value of emf be affected if the number of spokes were increased.

A short bar magnet placed on a horizontal plane has its axis aligned along the magnetic north- south direction . Null points are found on the magnet . The earth's magnetic field at the place is 0.36G . What is the magnet at the total magnetic field on the normal bisector of the same distance as the null points (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 . )

Radius and number of turns of a circular coil are 10 cm and 25 respectively. What should be the curcrent through the coil that will produce a magnetic field of 6.28xx10^(-5)Wb*m^(-2) at its centre ?

A short magnet of magnetic moment 5.25xx10^(-2) JT^(-1) is placed with its axis perpendicular to the earth's field direction. At what distance from the centre of the magnet on (i) its normal bisector (ii) its axis, is the resultant field inclined at 45^@ with the earth's field. Magnitude of the earth's field at the place is 0.42G. Ignore length of the magnet in comparison to the distances involved.

A short bar magnet placed with its axis at 30^@ with a uniform external magnetic field of 0.25T experiences a torque of magnitude equal to 4.5xx10^(-2)Nm . What is the magnitude of magnetic moment?