Static Electricity 2000 Edition

D.1.47 Resistivity, Surface.
The electric resistance of the sur-
face of an insulator, in ohms per square, as measured between
the opposite sides of a square on the surface and whose value
in ohms is independent of the size of the square or the thick-
ness of the surface film.
D.1.48 Resistivity, Volume.
The resistance of a sample of
material, expressed in ohm-meters, having unit length and
unit cross-sectional area.
D.1.49 Spark.
A short-duration electric discharge due to a
sudden breakdown of air or some other insulating material
separating two conductors at different electric potentials,
accompanied by a momentary flash of light; also known as
electric spark, spark discharge, or sparkover.
D.1.50 Static Neutralizer, Alternating Current.
A static neu-
tralizer that uses an alternating current corona to generate
positive and negative ions. Ions from this equipment are
drawn from this ionizer to neutralize charged (usually insulat-
ing) surfaces. The frequency for AC static neutralizers is usu-
ally the line frequency (50/60 Hz).
D.1.51 Static Neutralizer, Electrically Powered.
A static neu-
tralizer that uses one or more electrified needles rigidly held
in a housing and a high-potential supply that powers the neu-
tralizer. Ion generation occurs in the air space surrounding
the highly charged needle points.
D.1.52 Surface-Charge Density.
The charge per unit area of
solid surface expressed in coulombs per square meter. In air,
the maximum surface charge density before air breakdown
occurs is 2.65 
× 10
−5
C/m
2
. Only a fraction of this value is
achieved in most practical situations.
D.1.53 Surface Streamer.
A surface-to-wall discharge observed
on charged liquids during tanker filling, appearing as a flash up
to 30 cm long and accompanied by a crackling sound. The effec-
tive energy is unknown but is possibly as high as approximately
10 mJ. Surface streamers are also observed on tribocharged solid
surfaces, such as between aircraft windshields and metal air-
frame, where puncturing does not occur.