Concepts Of Physics MCQ Edition [Volume 2]PhysicsPermanent Magnets
A magnetic dipole having a magnetic moment of 1.44 A m ^2 is positioned horizontally such that its north pole points towards the north. Determine the location of the neutral point, given that the horizontal component of the earth's magnetic field is 18 T .
Options
- AAt a distance of 20 cm in the plane bisecting the dipole
- BAt a distance of 40 cm in the plane bisecting the dipole
- CAt a distance of 20 cm on the axis of the dipole
- DAt a distance of 40 cm on the axis of the dipole
Correct answer
A. At a distance of 20 cm in the plane bisecting the dipole
Step-by-step solution
When the north pole of a magnetic dipole points towards the geographic north, its magnetic field on the equatorial line (the plane bisecting the dipole) is directed towards the geographic south. Since the horizontal component of the earth's magnetic field B_H is directed towards the geographic north, the neutral points will lie on the equatorial line. At the neutral point, the magnetic field of the dipole equals B_H : B_ eq = B_H ₀ 4 M d^3 = B_H Substituting the given values: 10⁻⁷ 1.44 d^3 = 18 10⁻⁶ d^3 = 1.44 10⁻⁷