Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

magnetic separator
a device employing magnetic fields to separate magnetic materials from nonmagnetic ones.
magnetic stabilization
the act of purposely demagnetizing a magnet with reverse fields or a change in temperature so that no irreversible losses are experienced when the magnet operates under similar conditions in the field.
magnetic susceptibility
the ratio of the magnetization to the applied external field.

Tensor relationship between the magnetic field vector and the magnetization vector in a medium with no hysteresis; magnetization divided by the permeability of free space and the magnetic field in scalar media. It is an indicator of how easily a material is magnetized and has no units in the SI system of units (pure number).
magnetic suspension

See magnetic levitation
magnetic torque coupling
any device utilizing a magnetic field to transmit torque.
magnetic vector potential
an auxiliary field used to simplify electromagnetic computations. This field satisfies a wave equation, the curl of this field is related to the magnetic field intensity vector field, and the divergence of this field is specified by some gage which is to be specified in each problem.
magnetization curve

See hysteresis curve
magnetizing current
the current required to magnetize the different parts of a magnetic circuit. It is calculated as the ratio of the total magnetomotive force (F) and the number of turns (N). More or less in transformers, and AC synchronous and induction machines, the magnetizing current is the current through the magnetizing inductance. Denoted by Im,it is calculated as the ratio of the induced EMF across the magnetizing inductance to its magnetizing reactance Xm.
magneto plasma
a plasma medium that in the presence of a static magnetic field behaves like an anisotropic dielectric medium whose dielectric function is a tensor.
magnetohydrodynamic MHD machine
a form of electric machine in which a stream of electrically conductive gas or liquid is passed through pairs of orthogonally positioned magnetic poles and electrodes. In an MHD generator, the fluid is forced by the prime mover to produce a DC across the electrodes. In the MHD motor, a current across the electrodes through the fluid forces the stream to flow.
magneto-hydrodynamic (MHD) generator
a heat-to-electricity conversion device with an intermediate kinetic energy stage. In the MHD generator, a partially conducting gas is heated by a fuel-fired source or a nuclear reactor to convert the heat energy to kinetic energy, and then passed between the poles of an electromagnet, which converts some of the kinetic energy to electrical energy. The electrical energy is collected through a pair of electrodes situated in the gas channel.
magnetomotive force (MMF)
a magnetic circuit term referring to that phenomenon that pushes magnetic flux through the reluctance of the circuit path. MMF is analogous to the concept of electromotive force (voltage) in an electric circuit. For a magnetic core with a single coil of N turns, carrying current I, the MMF is NI, with units of amperes (sometimes expressed as ampere-turns).
magnetoresistance
the change in electrical resistance in a conducting element experiencing a change in applied magnetic field. This is most pronounced when the magnetic field is perpendicular to current flow.
magnetostriction
a change in the length of a ferromagnetic material as the flux changes under the influence of an applied magnetic field, or resulting from domain formation after cooling from above Curie temperature. In an AC device, the steel in the core expands and contracts twice each cycle, creating audible noise (e.g., transformer hum).
magnetostrictive smart material
one of a class of materials with self-adaptively modifiable elastic properties in response to a magnetic field applied in proportion to sensed stress-strain information.
magnetotransport
motion of electrons or holes in a conducting material in the presence of an applied magnetic field.
magnetron
any arrangement of magnets in a sputter deposition or etch system that provides the magnetic field required to trap electrons in closed loops near the cathode, thus enhancing deposition/etch rates.
main switch
a switch which controls all power to a building's wiring or other electric installation.
mains voltage
European term for the voltage at the secondary of the distribution transformer.
maintainability
the probability that an inoperable system will be restored to an operational state within the time t.
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