Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

discontinuity effect
an appropriate equivalent circuit model for discontinuities that have a tendency to disturb the electric and magnetic fields in their vicinity.
dissipation factor (DF)
the ratio of the effective series resistance of a capacitor to its reactance at a specified frequency measured in percentage.
See loss tangent
diversity selection
a form of diversity reception in which the receiver selects the strongest signal among the copies received. The weaker signals are simply ignored.
fault detection
based on circuit duplication and comparison. One module is designed using positive logic and the other module uses negative logic. This assures detecting common mode faults.
earth electrode system
a network of electrically interconnected rods, plates, mats, or grids installed for the purpose of establishing a low-resistance contact with earth. The design objective for resistance to earth of this subsystem should not exceed 10 Ω.
electric charge
a basic physical quantity that is a source of electromagnetic fields. The units of electric charge are coulombs.
electric charge density
the fundamental, macroscopic source of the electromagnetic field that quantifies the average number of discrete electric charges per unit volume. SI units are coulombs per cubic meter.
electric current density
a source vector in electromagnetics that quantifies the amount of electric charge crossing some cross-sectional area per unit time. The direction of the electric current density is in the direction of electric charge motion. SI units are amperes per square meter.
electric field
in a region of space, if a test charge q experiences a force F then the region is said to be characterized by an electric field of intensity E given by

E = F / q
electric field intensity
a force field that is a measure of the magnitude and direction of the force imparted upon a discrete charge normalized to the discrete charge's value. Depends on material characteristics. The units are volts per meter.

electric flux density
basic electromagnetic field quantity used to describe the effects of permeable matter to the electric field; it is expressed in SI units of coulombs per square meter.
electric furnace
a method of smelting metals and applying high heat for industrial processes which makes use of the heat from an electric arc struck between (typically) carbon electrodes.
electric permittivity
tensor relationship between the electric field vector and the electric displacement vector in a medium with no hysteresis; displacement divided by the electric field in scalar media.
electric polarization vector
an auxiliary vector in electromagnetics that accounts for the creation of atomic dipoles in a dielectric material due to an applied electric field. Macroscopically, the electric polarization vector is equal to the average number of electric dipole moments per unit volume. Mathematically, P = D - Є0E, where D is the electric flux density, E is the electric field intensity, and Є0 is the free space permittivity. SI units are coulombs per square meter.
electric susceptibility
tensor relationship between the electric field vector and the electric polarization vector in a medium with no hysteresis. It is the polarization divided by the permittivity of free space and the electric
field in scalar media.
electric vector potential
a vector function that is used to derive solutions for electric and magnetic fields.
electric vehicle
a vehicle powered by an electrical energy storage device such as batteries.
electrical degrees
a convenient way of representing the distance around the circumference of a machine with two poles spanning the entire 360O of the circumference,

Electrical Degree = Pairs of poles x-intercept Mechanical Degree
electrical network
a collection of interconnected electrical devices.
electrical tree
a microscopic cracking pattern which forms in the insulation of electric power cables which are not exposed to water See tree, water tree.
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