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.
Right hand grip rule: a current flowing in the direction of the white arrow produces a magnetic field shown by the red arrows.
A Solenoid with electric current running through it behaves like a magnet.
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.
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

Vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials.

- 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.

101 related topics

Alpha

Lorentz force acting on fast-moving charged particles in a bubble chamber. Positive and negative charge trajectories curve in opposite directions.

Lorentz force

Combination of electric and magnetic force on a point charge due to electromagnetic fields.

Combination of electric and magnetic force on a point charge due to electromagnetic fields.

Lorentz force acting on fast-moving charged particles in a bubble chamber. Positive and negative charge trajectories curve in opposite directions.
Lorentz' theory of electrons. Formulas for the Lorentz force (I, ponderomotive force) and the Maxwell equations for the divergence of the electrical field E (II) and the magnetic field B (III), La théorie electromagnétique de Maxwell et son application aux corps mouvants, 1892, p. 451. V is the velocity of light.
Charged particle drifts in a homogeneous magnetic field. (A) No disturbing force (B) With an electric field, E (C) With an independent force, F (e.g. gravity) (D) In an inhomogeneous magnetic field, grad H
Right-hand rule for a current-carrying wire in a magnetic field B
Lorentz force -image on a wall in Leiden
Lorentz force -image on a wall in Leiden

and a magnetic field

A simple electromagnet consisting of a coil of wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created.  The strength of magnetic field generated is proportional to the amount of current through the winding.

Electromagnet

A simple electromagnet consisting of a coil of wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created.  The strength of magnetic field generated is proportional to the amount of current through the winding.
Magnetic field produced by a solenoid (coil of wire). This drawing shows a cross section through the center of the coil. The crosses are wires in which current is moving into the page; the dots are wires in which current is moving up out of the page.
Industrial electromagnet lifting scrap iron, 1914
Current (I) through a wire produces a magnetic field (B). The field is oriented according to the right-hand rule.
The magnetic field lines of a current-carrying loop of wire pass through the center of the loop, concentrating the field there
The magnetic field generated by passing a current through a coil
Cross section of lifting electromagnet like that in above photo, showing cylindrical construction. The windings (C) are flat copper strips to withstand the Lorentz force of the magnetic field. The core is formed by the thick iron housing (D) that wraps around the windings.
Large aluminum busbars carrying current into the electromagnets at the LNCMI (Laboratoire National des Champs Magnétiques Intenses) high field laboratory.
The most powerful electromagnet in the world, the 45 T hybrid Bitter-superconducting magnet at the US National High Magnetic Field Laboratory, Tallahassee, Florida, USA
A hollow tube type of explosively pumped flux compression generator. The hollow copper tube acts like a single turn secondary winding of a transformer; when the pulse of current from the capacitor in the windings creates a pulse of magnetic field, this creates a strong circumferential current in the tube, trapping the magnetic field lines within. The explosives then collapse the tube, reducing its diameter, and the field lines are forced closer together increasing the field.

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current.

Computer simulation of Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of Earth is centered and vertical. The dense clusters of lines are within Earth's core.

Earth's magnetic field

Computer simulation of Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of Earth is centered and vertical. The dense clusters of lines are within Earth's core.
Common coordinate systems used for representing the Earth's magnetic field.
Relationship between Earth's poles. A1 and A2 are the geographic poles; B1 and B2 are the geomagnetic poles; C1 (south) and C2 (north) are the magnetic poles.
The movement of Earth's North Magnetic Pole across the Canadian arctic.
An artist's rendering of the structure of a magnetosphere. 1) Bow shock. 2) Magnetosheath. 3) Magnetopause. 4) Magnetosphere. 5) Northern tail lobe. 6) Southern tail lobe. 7) Plasmasphere.
Background: a set of traces from magnetic observatories showing a magnetic storm in 2000.
Globe: map showing locations of observatories and contour lines giving horizontal magnetic intensity in μ T.
Estimated declination contours by year, 1590 to 1990 (click to see variation).
Strength of the axial dipole component of Earth's magnetic field from 1600 to 2020.
Geomagnetic polarity during the late Cenozoic Era. Dark areas denote periods where the polarity matches today's polarity, light areas denote periods where that polarity is reversed.
Variations in virtual axial dipole moment since the last reversal.
A schematic illustrating the relationship between motion of conducting fluid, organized into rolls by the Coriolis force, and the magnetic field the motion generates.
A model of short-wavelength features of Earth's magnetic field, attributed to lithospheric anomalies
Example of a quadrupole field. This can also be constructed by moving two dipoles together.

Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun.

Electric field of a positive and a negative point charge

Electric charge

Physical property of matter that causes it to experience a force when placed in an electromagnetic field.

Physical property of matter that causes it to experience a force when placed in an electromagnetic field.

Electric field of a positive and a negative point charge
Diagram showing field lines and equipotentials around an electron, a negatively charged particle. In an electrically neutral atom, the number of electrons is equal to the number of protons (which are positively charged), resulting in a net zero overall charge
Coulomb's torsion balance

A moving charge also produces a magnetic field.

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.

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

Vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material.

Vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material.

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.

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

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.

Magnetic field lines visualized using iron filings. When a piece of paper is sprinkled with iron filings and placed above a bar magnet, the filings align according to the direction of the magnetic field, forming arcs.

Quantum field theory

Theoretical framework that combines classical field theory, special relativity, and quantum mechanics.

Theoretical framework that combines classical field theory, special relativity, and quantum mechanics.

Magnetic field lines visualized using iron filings. When a piece of paper is sprinkled with iron filings and placed above a bar magnet, the filings align according to the direction of the magnetic field, forming arcs.
Elementary particles of the Standard Model: six types of quarks, six types of leptons, four types of gauge bosons that carry fundamental interactions, as well as the Higgs boson, which endow elementary particles with mass.
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The theory of classical electromagnetism was completed in 1864 with Maxwell's equations, which described the relationship between the electric field, the magnetic field, electric current, and electric charge.

Countries using the metric (SI), imperial, and US customary systems as of 2019.

International System of Units

Modern form of the metric system and the world's most widely used system of measurement.

Modern form of the metric system and the world's most widely used system of measurement.

Countries using the metric (SI), imperial, and US customary systems as of 2019.
Arrangement of the principal measurements in physics based on the mathematical manipulation of length, time, and mass.
While not an SI-unit, the litre may be used with SI units. It is equivalent to (10 cm)3 = (1 dm)3 = 10−3 m3.
In the expression of acceleration due to gravity, a space separates the value and the units, both the 'm' and the 's' are lowercase because neither the metre nor the second are named after people, and exponentiation is represented with a superscript '2'.
Cover of brochure The International System of Units
Silicon sphere for the Avogadro project used for measuring the Avogadro constant to a relative standard uncertainty of 2 or less, held by Achim Leistner
Reverse dependencies of the SI base units on seven physical constants, which are assigned exact numerical values in the 2019 redefinition. Unlike in the previous definitions, the base units are all derived exclusively from constants of nature. Arrows are shown in the opposite direction compared to typical dependency graphs, i.e..
Stone marking the Austro-Hungarian/Italian border at Pontebba displaying myriametres, a unit of 10 km used in Central Europe in the 19th century (but since deprecated)
Closeup of the National Prototype Metre, serial number 27, allocated to the United States

The first letter of symbols for units derived from the name of a person is written in upper case; otherwise, they are written in lower case. E.g., the unit of pressure is named after Blaise Pascal, so its symbol is written "Pa", but the symbol for mole is written "mol". Thus, "T" is the symbol for tesla, a measure of magnetic field strength, and "t" the symbol for tonne, a measure of mass. Since 1979, the litre may exceptionally be written using either an uppercase "L" or a lowercase "l", a decision prompted by the similarity of the lowercase letter "l" to the numeral "1", especially with certain typefaces or English-style handwriting. The American NIST recommends that within the United States "L" be used rather than "l".

A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.

Superconductivity

A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.
A high-temperature superconductor levitating above a magnet
"Top: Periodic table of superconducting elemental solids and their experimental critical temperature (T). Bottom: Periodic table of superconducting binary hydrides (0–300 GPa). Theoretical predictions indicated in blue and experimental results in red."
Electric cables for accelerators at CERN. Both the massive and slim cables are rated for 12,500 A. Top: regular cables for LEP; bottom: superconductor-based cables for the LHC
Cross section of a preform superconductor rod from abandoned Texas Superconducting Super Collider (SSC).
Behavior of heat capacity (cv, blue) and resistivity (ρ, green) at the superconducting phase transition
Heike Kamerlingh Onnes (right), the discoverer of superconductivity. Paul Ehrenfest, Hendrik Lorentz, Niels Bohr stand to his left.
Timeline of superconducting materials. Colors represent different classes of materials:

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material.