A magnetic dipole is under the influence of two magnetic fields. The angle between the field directions is 60°, and one of the fields has a magnitude of 1.2 × 10–2 T. If the dipole comes to stable equilibrium at an angle of 15° with this field, what is the magnitude of the other field?
A magnetic dipole is under the influence of two magnetic fields. The angle between the field directions is 60°, and one of the fields has a magnitude of 1.2 × 10–2 T. If the dipole comes to stable equilibrium at an angle of 15° with this field, what is the magnitude of the other field?

Answer-

Magnitude of one of the magnetic field is given by B1 = 1.2 × 10–2 T

Suppose that the magnitude of the other field is B2

And the angle between the field is given, θ = 60°

We are givenknow that at stable equilibrium, the angle between the dipole and the field B1, θ1 = 15°

Then the angle between the dipole and the field B2 can be written as –

θ2 =θ – θ1 = 45°

now, the torque due to the field B1 = the torque due to the field B2

Therefore, we get –

MB1 sin θ1 = MB2 sin θ2

where , M represents the magnetic moment of the dipole. So, we have –

    \[{{B}_{2}}=\frac{M{{B}_{1}}sin~{{\theta }_{1}}}{M~sin~{{\theta }_{2}}}\]

    \[=\frac{(1.2\times {{10}^{2}})x\sin {{15}^{\circ }}}{\sin {{45}^{\circ }}}=4.39\times {{10}^{-3}}T\]

Therefore, magnetic field due to the other magnetic field is 4.39 x 10-3 T.