A dip circle is taken togeomagnetic equator. The needle is allowed to move in a vertical plane perpendicular to the magnetic meridian. The needle will stayain horizontal direction onlybin vertical direction onlycin any direction except vertical and horizontaldin any direction it is released

A dip circle is taken togeomagnetic equator. The needle is allowed to move in a vertical plane perpendicular to the magnetic meridian. The needle will stayvertical direction because the horizontal component B_His perpendicular to this plane and hence does not take part in rotating the needle. The needle is aligned with the Vertical componenet B_V.