The angle of dip at equator is

The correct answer is Option (4) → zero

The angle of dip \( \delta \) is the angle that the earth's total magnetic field \( B_E \) makes with the horizontal, so the horizontal and vertical components are \( H = B_E\cos\delta \) and \( V = B_E\sin\delta \).

At the magnetic equator the field lines of the earth are parallel to the surface, so the field is purely horizontal and \( V = 0 \).

    \( \tan\delta = \frac{V}{H} = 0 \Rightarrow \delta = 0 \)