Magnetism is a phenomenon related to magnetic fields , which stem from moving electric charges, such as an electric current, charged particles in space, or an electron's motion in an atomic orbital. Elementary particles, like electrons, possess an intrinsic property called spin, also associated with magnetism. Magnetic fields exert forces on other magnetic objects and moving charges, leading to attraction or repulsion. These fields are depicted as continuous lines of force, or magnetic flux, emerging from north-seeking magnetic poles and entering south-seeking magnetic poles. Materials exhibit varying magnetic behaviors. Diamagnetic materials are weakly repelled by magnets, while paramagnetic materials, like chromium, are weakly attracted. Ferromagnetic materials, including iron, nickel, and cobalt, are strongly drawn to magnets and can be permanently magnetized.

What are magnets and how do they work?

Magnets are materials that can attract iron and produce a magnetic field outside themselves. This field, arising from moving electric charges, exerts forces on other magnetic objects and moving charges, leading to attraction or repulsion. Magnetic fields are represented by continuous lines of force, or magnetic flux, emerging from north-seeking magnetic poles and entering south-seeking poles. Different materials display varying degrees of magnetism. Most are diamagnetic and are weakly repelled by magnets. Paramagnetic materials, like chromium, are weakly attracted. Ferromagnetic materials, including iron, nickel, and cobalt, are strongly attracted and can be permanently magnetized. Magnetization involves aligning magnetic domains within a ferromagnetic material. When a magnetizing field is applied, these domains reorient, and the alignment can be temporary or permanent.

What is a magnetic field?

A magnetic field is a vector field near a magnet, electric current, or changing electric field where magnetic forces can be observed. Magnetic fields, such as Earth's, cause magnetic compass needles and other permanent magnets to align with the field's direction. Magnetic fields force moving, electrically charged particles into circular or helical paths. This force, exerted on electric currents in wires within a magnetic field, is the basis for electric motors. Magnetic fields are measured in units of tesla (T).

What are the north and south poles of a magnet?

The magnetic poles are regions at each end of a magnet where the external magnetic field is strongest. A magnet's north magnetic pole is the end that seeks the north, while the south magnetic pole is the end that seeks the south. The north and south poles attract each other, while like poles repel. If a magnet is broken in half, each half will have its own north and south pole.

How is the Earth like a giant magnet?

Earth acts like a giant magnet due to the movement of its electrically conducting liquid outer core. This motion generates electric currents in the presence of an existing magnetic field, which, in turn, produces a secondary magnetic field. The two fields combine, resulting in a stronger magnetic field that aligns with Earth's rotation axis. This process, known as the geomagnetic dynamo , is driven by heat from the freezing of the liquid core and possibly from radioactive elements. The Coriolis force introduces twists in the fluid motion, further contributing to the generation of the magnetic field. Earth's magnetic field is primarily dipolar, meaning it has two poles, like a simple bar magnet.

How are magnetism and electricity related?

Electromagnetism is the science of charge, forces, and fields associated with charge. Electricity and magnetism were once viewed as separate phenomena until the 19th century, when they were finally understood as interrelated. In 1820, Hans Christian Ørsted discovered that electric currents produce magnetic effects, linking electricity and magnetism. Michael Faraday later found that a changing magnetic field could produce an electric current. James Clerk Maxwell's theory then unified these concepts, showing that electric and magnetic fields travel together as electromagnetic waves, like light. Electric forces are produced by electric charges, whether at rest or in motion. Magnetic forces, however, are produced only by moving charges and act solely on charges in motion. A magnetic field influences only those charges that are already in motion and is transmitted by the magnetic field.

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Images & Videos

Diagram showing a circular loop of wire with an electric current, surrounded by curved blue lines representing magnetic field lines that loop around the wire and pass through its center.

Diagram showing a segment of wire carrying electric current, with labeled axes and arrows indicating the direction and magnitude of the magnetic field at various points around the wire. The wire runs horizontally, and magnetic field vectors are shown at numbered positions, illustrating how the field varies with distance and orientation.

Two diagrams show the magnetic field around a long straight wire carrying current. Panel A presents an end view with concentric circular field lines around the wire, current flowing toward the viewer. Panel B shows a three-dimensional view with the wire angled across the image and circular magnetic field lines surrounding it.

Diagram showing magnetic field lines around a small horizontal current loop at the center, with arrows indicating the field direction created by a clockwise current when viewed from above.

Diagram showing the magnetic force on moving charges: positive and negative charges move along the y-axis in a magnetic field pointing up the z-axis, with force vectors perpendicular to both velocity and field direction.

Diagram showing the right-hand rule for magnetic force: a hand with fingers pointing upward represents the magnetic field direction, the thumb points right for current direction, and the palm faces the direction of the resulting force. A coordinate system and arrows illustrate these directions.

Diagram showing four pairs of current loops with arrows indicating current direction and magnetic dipole moment. The diagram labels each pair as causing either attraction or repulsion based on the relative orientation of the loops.

Diagram showing four pairs of small bar magnets in different orientations: opposite poles facing attract, like poles facing repel, with labels indicating attraction or repulsion due to magnetism.

Diagram showing a small copper sample suspended between the north and south poles of an electromagnet, with magnetic field lines concentrated around the sample in an inhomogeneous magnetic field.

Diagram of an electromagnet featuring a coil of wire wound around a circular iron core with a visible small gap, illustrating a toroidal winding used to generate magnetism.

At a Glance

magnetism summary

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Written by

Edwin KashyAll

Fact-checked by

Britannica Editors

Last updated

Oct. 30, 2026 •History

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magnetism, phenomenon associated with magnetic fields, which arise from the motion of electric charges. This motion can take many forms. It can be an electric current in a conductor or charged particles moving through space, or it can be the motion of an electron in an atomic orbital. Magnetism is also associated with elementary particles, such as the electron, that have a property called spin.

Fundamentals

Basic to magnetism are magnetic fields and their effects on matter, as, for instance, the deflection of moving charges and torques on other magnetic objects. Evidence for the presence of a magnetic field is the magnetic force on charges moving in that field; the force is at right angles to both the field and the velocity of the charge. This force deflects the particles without changing their speed. The deflection can be observed in the torque on a compass needle that acts to align the needle with the magnetic field of Earth. The needle is a thin piece of iron that has been magnetized—i.e., a small bar magnet. One end of the magnet is called a north pole and the other end a south pole. The force between a north and a south pole is attractive, whereas the force between like poles is repulsive. The magnetic field is sometimes referred to as magnetic induction or magnetic flux density; it is always symbolized by B. Magnetic fields are measured in units of tesla (T). (Another unit of measure commonly used for B is the gauss, though it is no longer considered a standard unit. One gauss equals 10⁻⁴ tesla.)

A fundamental property of a magnetic field is that its flux through any closed surface vanishes. (A closed surface is one that completely surrounds a volume.) This is expressed mathematically by div B = 0 and can be understood physically in terms of the field lines representing B. These lines always close on themselves, so that if they enter a certain volume at some point, they must also leave that volume. In this respect, a magnetic field is quite different from an electric field. Electric field lines can begin and end on a charge, but no equivalent magnetic charge has been found in spite of many searches for so-called magnetic monopoles.

The most common source of magnetic fields is the electric current loop. It may be an electric current in a circular conductor or the motion of an orbiting electron in an atom. Associated with both these types of current loops is a magnetic dipole moment, the value of which is iA, the product of the current i and the area of the loop A. In addition, electrons, protons, and neutrons in atoms have a magnetic dipole moment associated with their intrinsic spin; such magnetic dipole moments represent another important source of magnetic fields. A particle with a magnetic dipole moment is often referred to as a magnetic dipole. (A magnetic dipole may be thought of as a tiny bar magnet. It has the same magnetic field as such a magnet and behaves the same way in external magnetic fields.) When placed in an external magnetic field, a magnetic dipole can be subjected to a torque that tends to align it with the field; if the external field is not uniform, the dipole also can be subjected to a force.

All matter exhibits magnetic properties to some degree. When placed in an inhomogeneous field, matter is either attracted or repelled in the direction of the gradient of the field. This property is described by the magnetic susceptibility of the matter and depends on the degree of magnetization of the matter in the field. Magnetization depends on the size of the dipole moments of the atoms in a substance and the degree to which the dipole moments are aligned with respect to each other. Certain materials, such as iron, exhibit very strong magnetic properties because of the alignment of the magnetic moments of their atoms within certain small regions called domains. Under normal conditions, the various domains have fields that cancel, but they can be aligned with each other to produce extremely large magnetic fields. Various alloys, like NdFeB (an alloy of neodymium, iron, and boron), keep their domains aligned and are used to make permanent magnets. The strong magnetic field produced by a typical three-millimetre-thick magnet of this material is comparable to an electromagnet made of a copper loop carrying a current of several thousand amperes. In comparison, the current in a typical light bulb is 0.5 ampere. Since aligning the domains of a material produces a magnet, disorganizing the orderly alignment destroys the magnetic properties of the material. Thermal agitation that results from heating a magnet to a high temperature destroys its magnetic properties.

Magnetic fields vary widely in strength. Some representative values are given in the Table.

Typical magnetic fields
inside atomic nuclei	10¹¹ T
in superconducting solenoids	20 T
in a superconducting coil cyclotron	5 T
near a small ceramic magnet	0.1 T
Earth's field at the Equator	4(10⁻⁵) T
in interstellar space	2(10⁻¹⁰) T

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