The shape of the magnetic field produced by a horseshoe magnet is revealed by the orientation of iron filings sprinkled on a piece of paper above the magnet.
An electrostatic analog for a magnetic moment: two opposing charges separated by a finite distance.
Right hand grip rule: a current flowing in the direction of the white arrow produces a magnetic field shown by the red arrows.
Image of a solenoid
A Solenoid with electric current running through it behaves like a magnet.
Magnetic field lines around a "magnetostatic dipole". The magnetic dipole itself is located in the center of the figure, seen from the side, and pointing upward.
A sketch of Earth's magnetic field representing the source of the field as a magnet. The south pole of the magnetic field is near the geographic north pole of the Earth.
The magnetic field of a current loop
One of the first drawings of a magnetic field, by René Descartes, 1644, showing the Earth attracting lodestones. It illustrated his theory that magnetism was caused by the circulation of tiny helical particles, "threaded parts", through threaded pores in magnets.
Hans Christian Ørsted, Der Geist in der Natur, 1854

In electromagnetism, the magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field.

- Magnetic moment

Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin.

- Magnetic field
The shape of the magnetic field produced by a horseshoe magnet is revealed by the orientation of iron filings sprinkled on a piece of paper above the magnet.

11 related topics

Alpha

A "horseshoe magnet" made of alnico, an iron alloy. The magnet, made in the shape of a horseshoe, has the two magnetic poles close together. This shape creates a strong magnetic field between the poles, allowing the magnet to pick up a heavy piece of iron.

Magnet

A "horseshoe magnet" made of alnico, an iron alloy. The magnet, made in the shape of a horseshoe, has the two magnetic poles close together. This shape creates a strong magnetic field between the poles, allowing the magnet to pick up a heavy piece of iron.
Magnetic field lines of a solenoid electromagnet, which are similar to a bar magnet as illustrated below with the iron filings
Iron filings that have oriented in the magnetic field produced by a bar magnet
Field of a cylindrical bar magnet computed accurately
Hard disk drives record data on a thin magnetic coating
Magnetic hand separator for heavy minerals
Magnets have many uses in toys. M-tic uses magnetic rods connected to metal spheres for construction.
A stack of ferrite magnets
Ovoid-shaped magnets (possibly Hematine), one hanging from another
Field lines of cylindrical magnets with various aspect ratios

A magnet is a material or object that produces a magnetic field.

The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces.

Helium Vector Magnetometer (HVM) of the Pioneer 10 and 11 spacecraft

Magnetometer

Helium Vector Magnetometer (HVM) of the Pioneer 10 and 11 spacecraft
The Magnetometer experiment for the Juno orbiter for Juno can be seen here on the end of a boom. The spacecraft uses two fluxgate magnetometers. (see also Magnetometer (Juno))
The compass is a simple type of magnetometer.
Coast and Geodetic Survey Magnetometer No. 18.
A uniaxial fluxgate magnetometer
A fluxgate compass/inclinometer
Aust.-Synchrotron,-Quadrupole-Magnets-of-Linac,-14.06.2007
A Diamond DA42 light aircraft, modified for aerial survey with a nose-mounted boom containing a magnetometer at its tip
Tri-axis Electronic Magnetometer by AKM Semiconductor, inside Motorola Xoom
Ground surveying in Surprise Valley, Cedarville, California

A magnetometer is a device that measures magnetic field or magnetic dipole moment.

A magnet made of alnico, a ferromagnetic iron alloy, with its keeper

Ferromagnetism

Basic mechanism by which certain materials form permanent magnets, or are attracted to magnets.

Basic mechanism by which certain materials form permanent magnets, or are attracted to magnets.

A magnet made of alnico, a ferromagnetic iron alloy, with its keeper
Electromagnetic dynamic magnetic domain motion of grain-oriented electrical silicon steel
Kerr micrograph of metal surface showing magnetic domains, with red and green stripes denoting opposite magnetization directions
Moving domain walls in a grain of silicon steel caused by an increasing external magnetic field in the "downward" direction, observed in a Kerr microscope. White areas are domains with magnetization directed up, dark areas are domains with magnetization directed down.

Permanent magnets (materials that can be magnetized by an external magnetic field and remain magnetized after the external field is removed) are either ferromagnetic or ferrimagnetic, as are the materials that are noticeably attracted to them.

The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces.

When the microscopic currents induced by the magnetization (black arrows) do not balance out, bound volume currents (blue arrows) and bound surface currents (red arrows) appear in the medium.

Magnetization

When the microscopic currents induced by the magnetization (black arrows) do not balance out, bound volume currents (blue arrows) and bound surface currents (red arrows) appear in the medium.

In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material.

Net magnetization results from the response of a material to an external magnetic field.

The magnetic field of a sphere with a north magnetic pole at the top and a south magnetic pole at the bottom. By comparison, Earth has a south magnetic pole near its north geographic pole and a north magnetic pole near its south pole.

Dipole

Dipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity.

Dipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity.

The magnetic field of a sphere with a north magnetic pole at the top and a south magnetic pole at the bottom. By comparison, Earth has a south magnetic pole near its north geographic pole and a north magnetic pole near its south pole.
Contour plot of the electrostatic potential of a horizontally oriented electrical dipole of infinitesimal size. Strong colors indicate highest and lowest potential (where the opposing charges of the dipole are located).
Electric field lines of two opposing charges separated by a finite distance.
Magnetic field lines of a ring current of finite diameter.
Field lines of a point dipole of any type, electric, magnetic, acoustic, etc.
The linear molecule CO2 has a zero dipole as the two bond dipoles cancel.
The bent molecule H2O has a net dipole. The two bond dipoles do not cancel.
Resonance Lewis structures of the ozone molecule
Modulus of the Poynting vector for an oscillating electric dipole (exact solution). The two charges are shown as two small black dots.

For the magnetic (dipole) current loop, the magnetic dipole moment points through the loop (according to the right hand grip rule), with a magnitude equal to the current in the loop times the area of the loop.

Similar to magnetic current loops, the electron particle and some other fundamental particles have magnetic dipole moments, as an electron generates a magnetic field identical to that generated by a very small current loop.

Experimental setup

Einstein–de Haas effect

Experimental setup

The Einstein–de Haas effect is a physical phenomenon in which a change in the magnetic moment of a free body causes this body to rotate.

The experiments involve a cylinder of a ferromagnetic material suspended with the aid of a thin string inside a cylindrical coil which is used to provide an axial magnetic field that magnetizes the cylinder along its axis.

When liquid oxygen is poured from a beaker into a strong magnet, the oxygen is temporarily contained between the magnetic poles owing to its paramagnetism.

Paramagnetism

When liquid oxygen is poured from a beaker into a strong magnet, the oxygen is temporarily contained between the magnetic poles owing to its paramagnetism.
Idealized Curie–Weiss behavior; N.B. TC=θ, but TN is not θ. Paramagnetic regimes are denoted by solid lines. Close to TN or TC the behavior usually deviates from ideal.

Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field.

The magnetic moment induced by the applied field is linear in the field strength and rather weak.

Illustration of a magnet with four magnetic closure domains. The magnetic charges contributed by each domain are pictured at one domain wall. The charges balance, so the total charge is zero.

Demagnetizing field

[[File:VFPt magnets BHM.svg|thumb|Comparison of magnetic field (flux density)

[[File:VFPt magnets BHM.svg|thumb|Comparison of magnetic field (flux density)

Illustration of a magnet with four magnetic closure domains. The magnetic charges contributed by each domain are pictured at one domain wall. The charges balance, so the total charge is zero.

The demagnetizing field, also called the stray field (outside the magnet), is the magnetic field (H-field) generated by the magnetization in a magnet.

The term demagnetizing field reflects its tendency to act on the magnetization so as to reduce the total magnetic moment.

It is impossible to make magnetic monopoles from a bar magnet. If a bar magnet is cut in half, it is not the case that one half has the north pole and the other half has the south pole. Instead, each piece has its own north and south poles. A magnetic monopole cannot be created from normal matter such as atoms and electrons, but would instead be a new elementary particle.

Magnetic monopole

Hypothetical elementary particle that is an isolated magnet with only one magnetic pole .

Hypothetical elementary particle that is an isolated magnet with only one magnetic pole .

It is impossible to make magnetic monopoles from a bar magnet. If a bar magnet is cut in half, it is not the case that one half has the north pole and the other half has the south pole. Instead, each piece has its own north and south poles. A magnetic monopole cannot be created from normal matter such as atoms and electrons, but would instead be a new elementary particle.

However, an improved understanding of electromagnetism in the nineteenth century showed that the magnetism of lodestones was properly explained not by magnetic monopole fluids, but rather by a combination of electric currents, the electron magnetic moment, and the magnetic moments of other particles.

First, electric currents create magnetic fields according to Ampère's law.

Schematic diagram depicting the spin of the neutron as the black arrow and magnetic field lines associated with the neutron magnetic moment. The neutron has a negative magnetic moment. While the spin of the neutron is upward in this diagram, the magnetic field lines at the center of the dipole are downward.

Spin (physics)

Intrinsic form of angular momentum carried by elementary particles, and thus by composite particles and atomic nuclei.

Intrinsic form of angular momentum carried by elementary particles, and thus by composite particles and atomic nuclei.

Schematic diagram depicting the spin of the neutron as the black arrow and magnetic field lines associated with the neutron magnetic moment. The neutron has a negative magnetic moment. While the spin of the neutron is upward in this diagram, the magnetic field lines at the center of the dipole are downward.
A single point in space can spin continuously without becoming tangled. Notice that after a 360-degree rotation, the spiral flips between clockwise and counterclockwise orientations. It returns to its original configuration after spinning a full 720°.
Wolfgang Pauli lecturing

The spin of a charged particle is associated with a magnetic dipole moment with a g-factor differing from 1. This could occur classically only if the internal charge of the particle were distributed differently from its mass.

These magnetic moments can be experimentally observed in several ways, e.g. by the deflection of particles by inhomogeneous magnetic fields in a Stern–Gerlach experiment, or by measuring the magnetic fields generated by the particles themselves.