What Is Magnetic Dipole and Moment

∟What Is Magnetic Dipole and Moment

This section provides a quick introduction of of magnetic dipole and its moment.

What Is Magnetic Dipole? A Magnetic Dipole is a mathematical model to represent an ideal magnetic field with key feature:

Has a pair of north pole and south pole located at the center of the field with zero distance.

What Is Magnetic Dipole Moment? A Magnetic Moment, μ (mu), is a vector value that represents two properties of a Magnetic Dipole:

The direction of the Magnetic Dipole running from its south pole to its north pole.
The strength of the Magnetic Dipole.

Wire Loop as Magnetic Dipole - The magnetic field created by the running current in a wire loop can be approximated as a magnetic dipole, if the loop is small or we only focus on areas far away from the loop.

In this approximation, the magnitude of the magnetic dipole moment is proportional to both the current and the area of the loop:

        
where:
        I is the current
        A is the area of the loop

Solenoid as Magnetic Dipole - The magnetic field created by a solenoid can be approximated as a magnetic dipole, if we only focus on areas far away from the solenoid.

In this approximation, the magnitude of the magnetic dipole moment is proportional to the current, the area of a single loop and the number of loops:

        
where:
        N is the number of loops
        I is the current
        A is the area of the loop

Magnetic Bar as Magnetic Dipole - The magnetic field created by a magnetic bar can be approximated as a magnetic dipole, if we only focus on areas far away from the bar.

In this approximation, the magnitude of the magnetic dipole moment is proportional to the remanence and the volume of the magnetic bar:

        
where:
        B_r is the magnetic remanence of the bar 
        A is the cross-sectional area of the bar  
        L is the length of the bar
        μ₀ is the vacuum permeability (4π × 10^-7, or 1.2566 × 10^-6)

Magnetic Needle as Magnetic Dipole - The magnetic field created by a magnetic needle (e.g. the one used in a compass) can be approximated as a magnetic dipole, if we only focus on areas far away from the needle.