Question

In a deflection magnetometer, the external magnet should be replaced:

• A. always in the direction of resultant of earth
• B. always with its axis along E-W
• C. along N-S in tan A position
• D. always along N-S

Answer 1

Answer: (B)

always with its axis along E-W

Answer 2

The tangent law on which the principle of working of a deflection magnetometer is based, slates, when two magnetic field F and H act as right angles, then these two fields defects through an angle $\theta$ which is related. $F=H\sin \theta$ Earths field is always along the directions of East West direction, therefore the magnet must always be placed with its axis along the direction of East West.