1) Charging by friction occurs when two neutral objects are rubbed together, causing electrons to transfer between the objects. 2) Different materials gain or lose electrons at different rates when rubbed, as shown by the electrostatic series which ranks materials based on their tendency to gain or lose electrons. 3) When cotton and ebonite, which are near opposite ends of the electrostatic series, are rubbed together the ebonite gains electrons from the cotton, leaving the cotton positively charged and the ebonite negatively charged.

1. Friction and the Electrostatic Series
The simplest way to charge a neutral object
is by friction.
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2. Friction and the Electrostatic Series
Charging by friction is the transfer of e-
between 2 neutral objects that occurs when
they are rubbed together or touch.
Neutral Cotton
Neutral Ebonite
+-+-+
-+-+-

3. Friction and the Electrostatic Series
When rubbed together, different materials
lose or gain e- more easily than others.
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4. Friction and the Electrostatic Series
The Electrostatic Series ranks different materials
on their ability to gain or lose electrons.
Tendency to gain
Material Relative Charge
electrons
platinum, gold most likely Negative
rubber
ebonite
carbon, copper,
nickel
polyethylene
(plastic)
cotton
silk
nylon
fur or hair
wool
Glass least likely Positive +
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Acetate

5. Friction and the Electrostatic Series
Neutral Cotton Neutral Ebonite
+-+-+
-+-+-
What will happen when these are rubbed
together?
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6. Friction and the Electrostatic Series
Neutral Cotton
Rub
Rub Rub
+-+-+
Neutral Ebonite
-+-+-
Rub
e-move from
cotton into Rub
ebonite.
Rub

7. Friction and the Electrostatic Series
Results:
Positively
Charged Cotton Negatively
Charged Ebonite
+++
-+-+
* The number of + and – are conserved.
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8. Friction and the Electrostatic Series
Note: the + and signs do not represent the
actual number of positive and negative charges
(protons or electrons).
They represent a collection of charges (protons or
electrons).
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