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Detection of electric charges using an Electroscope

16 May

There are three modes of how we can electrifying an object: friction, conduction and induction.
Electrification by friction occurs when two surfaces are rubbed together. Examples of this were
discussed above when a positive charge was created by rubbing glass with silk and a negative
charge was created by rubbing rubber with fur. The following list details a larger portion of the
 triboelectric sequence. When any two substances shown in this list are rubbed together, the
top one will become positively charged while the lower one will become negatively charged. The
further apart the two substances are in the list, the greater the electrification.
+
Asbestos
Fur (rabbit)
Glass
Mica
Wool
Quartz
Fur (cat)
Lead
Silk
Human skin, Aluminum
Cotton
Wood
Amber
Copper, Brass
Rubber
Sulfur
Celluloid
India rubber
Charging by conduction means that the charging rod actually touches the electroscope’s knob.
Since there is contact, electrons from the knob would flow onto a positive rod or off of a negative rod.
Charging by conduction leaves the electroscope with a residual charge IDENTICAL to that of the
charging rod.
Charging by induction means that the charging rod is brought close to the electroscope’s knob but
NEVER touches it. If the electroscope is not grounded, it will remain neutral but be temporarily
polarized while the charging rod is in the immediate vicinity. That is, a positive rod will induce the
electrons in the scope to migrate to the knob. This redistribution of charge will result in the leaves
of the scope being positively charged
 

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