5.21. A magnetic dipole is under the influence of two magnetic fields. The angle between the field directions is , and one of the fields has a magnitude of T. If the dipole comes to stable equilibrium at an angle of with this field, what is the magnitude of the other field?
Given,
The magnitude of the first magnetic field, B1 = 1.2 × 10–2 T
The angle between the magnetic field directions, = 60°
The angle between the dipole and the magnetic field is = 15°
Let B2 be the magnitude of the second magnetic field and M be the magnetic dipole moment
Therefore, the angle between the dipole and the magnetic field B2 is = = 45°
Now, at rotational equilibrium,
The torque due to field B1 = Torque due to field B2
Hence the magnitude of the second magnetic field