Concepts Of Physics MCQ Edition [Volume 2]PhysicsPermanent Magnets
A magnetic dipole having a magnetic moment of 0.72 A m ^2 is placed horizontally such that its north pole points towards south. Determine the position of the neutral points, given that the horizontal component of the earth's magnetic field is 18 T .
Options
- AAt a distance of 15.9 cm on the equatorial line
- BAt a distance of 20 cm on the axial line
- CAt a distance of 20 cm on the equatorial line
- DAt a distance of 15.9 cm on the axial line
Correct answer
B. At a distance of 20 cm on the axial line
Step-by-step solution
When the north pole of a magnet points towards the geographic south, its magnetic moment M (directed from the south pole to the north pole of the magnet) points towards the geographic south. The earth's horizontal magnetic field B_H points towards the geographic north. On the axial line, the magnetic field of the dipole B_ axial is in the direction of M , which is towards the geographic south. Thus, B_ axial and B_H are in opposite directions, and neutral points are obtained on the axial line. At the neutral point,