ELECTRON: One of the fundamental constituents of atoms. The electron is a very small negatively charged particle
with a rest mass of approximately 1/1836 that of the hydrogen atom, or 9.107 x 10-28 gm. It has an electric charge of
4.802 x 10-10 statcoulomb (the electrostatic unit of charge). Electrons appear to be uniform in mass and charge.
ELECTRON CAPTURE (RT): A mode of radioactive decay in which a bound electron is captured by the nucleus of the
same atom, producing a vacancy in an inner emission of characteristic X-rays or auger electrons.
ELECTRON FOCUS (RT): The surface of the intersection of the electron beam and the anode of the X-ray tube.
ELECTRON GUN (RT): A device in which electrons (usually liberated from a hot filament) are focused and
accelerated, and from which they are emitted as a narrow beam.
ELECTRON PAIR (RT): An electron and a positron resulting from pair production.
ELECTRON RADIOGRAPHY (RT): The process whereby a photographic image of an object is produced by electron
radiation that has penetrated through the object.
ELECTRON VOLT: A unit of energy commonly used to express the energy of X-rays. One electron volt is the energy
gained by an electron when it is accelerated by a potential difference of 1 volt (1 eV = 1.60210 x 10-19 joule - SI).
ELECTROPLATING: Electrodepositing metal in an adherent method upon a metal object serving as a cathode.
Examples would be nickel chromium and cadmium deposits. Thicknesses under 0.005 do not interfere with magnetic
ELECTROSTATIC SPRAYING (PT): A technique of spraying wherein the material being sprayed is given a high
electrical charge, while the test piece is grounded.
ELEMENT: One of the 103 known chemical substances that cannot be divided into simpler substances by chemical
means. Examples: hydrogen, lead, and uranium.
ELEMENTARY PARTICLE: Originally a term applied to any particle that could not be further subdivided; now
applied only to protons, electrons, neutrons, antiparticles, and strange particles, but not to alpha particles and
ELONGATION: In tensile testing, the increase in the gage length, measured after fracture of the specimen within the
gage length, usually expressed as a percentage of the original gage length.
EMBRITTLEMENT: Reduction in the normal ductility of a metal due to a physical or chemical change.
EMBRYO/FETUS: The developing human organism, from conception until the time of birth.
EMISSIVITY: The energy emission rate usually expressed as r/c/hr @ 1 ft or mR/mc/hr @ 1 ft.
EMULSIFICATION (PT): The process of dispersing one liquid in a second immiscible liquid; the largest group of
emulsifying agents are soaps, detergents, and other compounds, whose basic structure is a paraffin chain terminating in
a polar group.
EMULSIFICATION TIME (PT): The time allowed for the emulsifier to act on the penetrant before the part is washed,
after emulsifier is applied as a separate step.
EMULSIFIER (PT): A liquid agent that must be applied to the non-water washable penetrant after the proper dwell
time has elapsed to permit water rinsing. This requires an additional step and a period of time must be allowed for the
combining to occur. A suspension of one liquid phase in another.