Static Electricity 2000 Edition

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STATIC ELECTRICITY
2000 Edition
FIGURE 4.1.8(a)
Typical charge generation by bulk motion 
of insulating materials. (Walmsley, 1992, p. 19.)
FIGURE 4.1.8(b)
Typical charge generation by atomization. 
(Walmsley, 1992, p. 19.)
4.1.9
Conductive materials can become charged when
brought near a highly charged surface. Electrons in the con-
ductive material are either drawn toward or forced away from
the region of closest approach to the charged surface, depend-
ing on the nature of the charge on that surface. If the conduc-
tive material is then touched to ground or to a third object,
additional electrons can pass to or from ground or the object.
If contact is then broken and the conductive material and
charged surface are separated, the charge on the isolated con-
ductive object changes. The net charge that is transferred is
called induced charge. [See Figures 4.1.9(a), (b), (c), and (d).]
4.1.10
The separation of charge on a neutral isolated conduc-
tor and its distribution near a charged insulating surface will
produce electrical stresses near the point of closest approach.
Sharp edges on the conductor can yield a localized electrical
breakdown of the gas stream, known as corona, or an electric
spark across the gap. Either of these events can transfer charge
between the materials, leaving the isolated conductor
charged. Such a transfer occurs, for example, when a person
wearing nonconductive shoes receives a static electric shock by
contacting the metal frame supporting a highly charged web.
As a result, the person acquires a net static electric charge and
can receive a second shock after leaving the area by touching
a grounded metal object, thereby allowing the acquired
charge to flow to earth.
4.1.11
Charge can also be imparted to a surface or into the
bulk of a material by directing a stream of electrons or ions
against it. If the surface is not conductive or is conductive but
isolated from ground, the charge delivered by the bombard-
ing stream will remain after the stream stops.
4.1.12
Charge can also be injected into a stream of noncon-
ductive fluid by submerging within the stream a pointed elec-
trode on which a high voltage has been impressed.