Magnetic field


In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges and magnetic dipoles, such as those in electric currents and magnets. Where such a field is present, magnetic force acts on other such bodies. All materials respond to a magnetic field to some degree, by opposing it or being attracted to it.

The direction of a magnetic field can be demonstrated with magnetic dipoles; magnetic dipoles in a magnetic field align themselves to be parallel with the field lines, as can be seen when iron filings are in the presence of a magnet. Unlike the electric field, the force exerted by a magnetic field on a charged particle is perpendicular to both the field and the velocity the particle. Magnetic fields also have an energy density proportional to the square of the field intensity. The intensity of the magnetic field has SI units of teslas.

For a closer look at the effects of a magnetic field, see under ferromagnetism, paramagnetism, diamagnetism, electromagnetism, and electromagnetic induction.