Question

Explain magnetic moment. Write its SI unit.

Hint:

Magnetic moment \(M = I \cdot A\), where \(I\) is current and \(A\) is area. SI unit = \(\text{A·m}^2\).

Answer 1

The magnetic moment (\(M\)) is a vector quantity that represents the strength and direction of a magnetic source, such as a magnetic dipole. It is defined as the product of the current (\(I\)) flowing through a loop and the area (\(A\)) of the loop: \[ M = I \cdot A \] Where: - \(I\) is the current in amperes (A), - \(A\) is the area of the loop in square meters (\(\text{m}^2\)). The magnetic moment determines how a magnetic object will interact with an external magnetic field. It tends to align with the field, and the torque experienced by the magnetic moment in the field is given by: \[ \tau = M \cdot B \cdot \sin(\theta) \] Where: - \(\tau\) is the torque,
- \(B\) is the magnetic field strength,
- \(\theta\) is the angle between the magnetic moment and the magnetic field.
The SI unit of magnetic moment is \(\text{Ampere-square meter (A·m}^2)\). It is also sometimes expressed in joules per tesla (J/T), as torque (joules) per unit magnetic field strength (tesla).
In summary, the magnetic moment describes the strength and orientation of a magnetic source, and its SI unit is \(\text{A·m}^2\).