If the bar magnet in Q. 8 is turned around by 180°, where will the new null points be located?
When a bar magnet is turned by 180°, then the null points are obtained on the equatorial line.So, magnetic field on the equatorial line at a distance d’ is given by
This magnetic field is equal to’ the horizontal component of the earths magnetic field,
As we know that, Magnetic field,
From Eqs. (i) and (ii), we
Thus, the null points are located on the equatorial line at a distance of 11.1 cm.