The horizontal component of earth's magnetic field is zero at a place where angle of dip is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 90^\circ \)
The angle of dip \( \delta \) is the angle that the earth's total magnetic field \( B_E \) makes with the horizontal. Its components are:
\( H = B_E\cos\delta \) (horizontal)
\( V = B_E\sin\delta \) (vertical)
The horizontal component vanishes when \( \cos\delta = 0 \), that is for \( \delta = 90^\circ \). The field is then purely vertical, as at the magnetic poles of the earth.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Magnetic Declination and Dip – “… This is known as the angle of dip (also known as inclination). Thus, dip is the angle that the total magnetic field BE of the earth makes with the surface of the earth. … The total magnetic field at P can be resolved into a horizontal component HE and a vertical component ZE. The angle that BE makes with HE is the angle of dip, I.”