a-b | c | d-f | g-j | k-m | n-p | r-s | t-z
DC or direct current Electrical circuits where the electricity flows in the same direction all the time (a battery produces DC)
Distribution In electric power systems, used to describe the lower voltages, used for distributing electricity locally, including into homes
E Usual abbreviation for the electric field
EA Electricity Association, the former trade association in the UK representing most electricity companies, now replaced by the Energy Networks Association ENA (EA can also stand for the Environment Agency)
Electric fields are produced by voltages, irrespective of how much current is flowing and indeed whether any current is flowing at all. The electric field is the region around a conductor where a force will be experienced by a charge.
Electrons. Fundamental particles carrying one negative charge each, which carry current in metals and many other materials
ELF. Accronym for Extremely Low Frequency, the scientific term for the power frequencies - 50 or 60 Hz - of the fields produced by the power system.
Elliptical polarisation If we have more than one source, e.g. a three-phase circuit, the field no longer has to oscillate along a straight line. It actually traces out an ellipse. This is known as “elliptical polarisation”.
Emdex name of a family of magnetic field instruments, available from Enertech Consultants in America.
EMFs Electric and magnetic fields. Sometimes also defined as electromagnetic fields, which usually means the same thing
Epidemiology The study of the patterns of diseases in a population, to try to determine their causes and to identify risk factors
EPRI Electric Power Research Institute, a research organisation in America. Many USA utilities subscribe to EPRI rather than perform their own research
Extremely Low Frequency. Defined as the range of frequencies from 30 to 300 Hz and therefore including the power frequencies of 50 or 60 Hz.
Far field The situation where you are far away from a source of fields. The electric and magnetic fields are coupled together to form radiation. Often the case at radiofrequencies but not at power frequencies
Field A very general concept in physics for a region of space where a quantity exists with a specific value at each point in the region. You can have a field of almost anything that varies over space: temperature, for instance, as well as the more common gravitational and electric and magnetic fields. The term “field” is, however, only in common use for things which are capable of exerting a force.
Fluxgate magnetometer A way of measuring magnetic fields. A magnetic core is deliberately driven into saturation in alternate directions at a high frequency. An external magnetic field introduces asymmetries which are detected.
Free radicals Highly reactive chemical species (part of a molecule) with an unpaired electron. The number of free radicals can sometimes be affected by magnetic fields.