Question

The torque on a bar magnet due to the earth's magnetic field is maximum when the axis of the magnet is

• A. Perpendicular to the field of the earth
• B. Parallel to the vertical component of the earth's field
• C. At an angle of 33^o with respect to the N-S direction
• D. Along the North-South (N-S) direction

Answer 1

Answer: (A)

Perpendicular to the field of the earth

Answer 2

Torque on a bar magnet in earths magnetic field (B_H) is $\tau = M B _ { H } \sin \theta$ τ will be maximum if sin θ = maximum i.e. θ = 90^o. Hence axis of the magnet is perpendicular to the field of earth.