Magnetostriction is a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. The effect was first identified in 1842 by James Joule when observing a sample of nickel. (Compare with electrostriction) Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ... Magnetic field lines shown by iron filings 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. ... 1842 was a common year starting on Saturday (see link for calendar). ... James Prescott Joule (December 24, 1818–October 11, 1889) was an English physicist, born in Salford, near Manchester. ... For other uses, see Nickel (disambiguation). ... Electrostriction is a property of all electrical non-conductors, or dielectrics, that produces a relatively slight change of shape, or mechanical deformation, under the application of an electric field. ...

This effect can cause losses due to frictional heating in susceptible ferromagnetic cores.

Explanation

Internally, ferromagnetic materials have a crystal structure that is divided into [[magnetic domain/domains], each of which is a region of uniform magnetic polarisation. When a magnetic field is applied, the boundaries between the domains shift and the domains rotate, both these effects causing a change in the material's dimensions. The reciprocal effect, the change of the susceptibility of a material when subjected to a mechanical stress, is called the Villari effect. Two other effects are related to magnetostriction: the Matteucci effect is the creation of a helical anisotropy of the susceptibility of a magnetostrictive material when subjected to a torque and the Wiedemann effect is the twisting of these materials when an helical magnetic field is applied to them. The Villari Reversal is the change in sign of the magnetostriction of iron from positive to negative when exposed to magnetic fields of approximately 40000 A/m (500 oersteds). Torque applied via an adjustable end wrench Relationship between force, torque, and momentum vectors in a rotating system In physics, torque (or often called a moment) can informally be thought of as rotational force or angular force which causes a change in rotational motion. ... For other uses, see Iron (disambiguation). ... The oersted is old CGS unit of magnetic field strength (or magnetic induction). ...

Magnetostrictive materials

Magnetostrictive materials can convert magnetic energy into kinetic energy, or the reverse, and are used to build actuators and sensors. The property can be quantified by the magnetostrictive coefficient, L, which is the fractional change in length as the magnetization of the material increases from zero to the saturation value. The effect is responsible for the familiar "electric hum" ( Listen (help· info)) which can be heard near transformers and high power electrical devices (depending on country, either 100 or 120 hertz, plus harmonics). The kinetic energy of an object is the extra energy which it possesses due to its motion. ... A three-dimensional actuator modelled using elastica theory. ... Not to be confused with censure, censer, or censor. ... For magnetic materials, saturation is the state when the material can not absorb a stronger magnetic field, such that an increase of magnetization produces no significant change in magnetic flux density. ... Spectrum of mains hum at 60 Hz Electric hum, mains hum, or power line hum is an audible oscillation at the frequency of the mains alternating current, which is usually 50 or 60 hertz depending on the local electric utility configuration (see Mains electricity). ... Image File history File links Mains hum 60 Hz. ... Image File history File links Mains hum 60 Hz. ... Figure 1:Three-phase pole-mounted step-down transformer. ... MHZ redirects here. ... In acoustics and telecommunication, the harmonic of a wave is a component frequency of the signal that is an integral multiple of the fundamental frequency. ...

Cobalt exhibits the largest room temperature magnetostriction of a pure element at 60 microstrain. Among alloys, the highest known magnetostriction is exhibited by Terfenol-D, (Ter for terbium, Fe for iron, NOL for Naval Ordnance Laboratory, and D for dysprosium). Terfenol-D, Tb_xDy_1-xFe₂, exhibits about 2000 microstrains in a field of 2 kOe (160 kA/m) at room temperature and is the most commonly used engineering magnetostrictive material [1]. This article is about the deformation of materials. ... Terfenol-D is an alloy of the formula Tb(0. ... General Name, Symbol, Number terbium, Tb, 65 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 158. ... For other uses, see Iron (disambiguation). ... The Naval Ordnance Laboratory (NOL), now disestablished, formerly located in White Oak, Maryland was the site of considerable work that had practical impact upon world technology. ... General Name, Symbol, Number dysprosium, Dy, 66 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Standard atomic weight 162. ... General Name, Symbol, Number terbium, Tb, 65 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Atomic mass 158. ... General Name, Symbol, Number dysprosium, Dy, 66 Chemical series lanthanides Group, Period, Block n/a, 6, f Appearance silvery white Standard atomic weight 162. ... For other uses, see Iron (disambiguation). ...

See also

• Electrostriction
• Piezoelectricity

Electrostriction is a property of all electrical non-conductors, or dielectrics, that produces a relatively slight change of shape, or mechanical deformation, under the application of an electric field. ... Piezoelectricity is the ability of some materials (notably crystals and certain ceramics) to generate an electric potential[1] in response to applied mechanical stress. ...

External links

• Magnetostriction
• Magnetostriction(2)
• Magnetostriction(3)
• Electricity is supposed to be the "silent servant". So why do transformers hum?