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In a uniform magnetic field B, the free energy F can be related to the magnetic moment M of the system as = where S is the entropy of the system and T is the temperature. Therefore, the magnetic moment can also be defined in terms of the free energy of a system as m = − ∂ F ∂ B | T . {\displaystyle m=\left.-{\frac {\partial F}{\partial B ...
The magnetic moment of an object is an intrinsic property and does not change with distance, and thus can be used to measure "how strong" a magnet is. For example, Earth possesses an enormous magnetic moment, however we are very distant from its center and experience only a tiny magnetic flux density (measured in tesla ) on its surface.
The magnetic moment is a vector: it has both a magnitude and direction. The direction of the magnetic moment points from the south to north pole of a magnet (inside the magnet). For example, the direction of the magnetic moment of a bar magnet, such as the one in a compass is the direction that the north poles points toward. In the physically ...
Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other.Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, magnetism is one of two aspects of electromagnetism.
Accordingly, physicists and engineers usually define magnetization as the quantity of magnetic moment per unit volume. [1] It is represented by a pseudovector M. Magnetization can be compared to electric polarization, which is the measure of the corresponding response of a material to an electric field in electrostatics.
Helium vector magnetometer (HVM) of the Pioneer 10 and 11 spacecraft. A magnetometer is a device that measures magnetic field or magnetic dipole moment.Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location.
The force is particularly sensitive to rotations of the magnets due to magnetic torque. The force on each magnet depends on its magnetic moment and the magnetic field [note 7] of the other. To understand the force between magnets, it is useful to examine the magnetic pole model given above.
The change in weight when the electromagnet is turned on is proportional to the susceptibility. Today, high-end measurement systems use a superconductive magnet. An alternative is to measure the force change on a strong compact magnet upon insertion of the sample. This system, widely used today, is called the Evans balance. [9]