Charging Objects
Key Terms
 Conductor  materials that can conduct electricity
 This means that they can carry the electric charge from one area to
another
 Examples: Metals! Salt water, human body
 Insulator  materials that do not conduct electricity
 This means that the charge will stay still (static)
 Examples: rubber, plastic, wood
Charging Objects
1. Charging by Contact
Charging by Friction
Charging by Conduction
2. Charging by Induction
Charging by Contact - Friction
Objects: Two Neutral Objects
Action: Rub together, electrons transfer from
one object to another
Outcome: One negative object, one positive object
The Electrostatic
Series
Material
Charge Tendency
Human Skin
Weak Tendency to
gain electrons
Rabbit Fur
Acetate
Glass
The object with the stronger
tendency to gain electrons will
become negatively charged.
Human hair
The object with the weaker tendency
to gain electrons will be positively
charged.
Cat fur
nylon
wool
Silk
Paper
Cotton
Wood
This chart is on page 473
Vinyl
Polyester
Ebonite
Strong Tendency to
gain electrons
Charge by Contact - Conduction
-5 charge
-3 charge
-4 charge
-4 charge
Objects: Two differently charged objects
Action: Two objects come in contact
with each other, electrons transfer
between objects
Outcome: Two objects share the same charge
Also, commonly seen between a charged and
neutral object
Metal Leaf Electroscope
Metal leaf electroscopes can be used the
detect charge
When a charged object comes in contact
with the metal knob, the charge moves to
the aluminum foil.
Why does this happen? The metal knob, stem and
foil all conduct electricity
Remember: Laws of Electric Charge
Grounding
Objects do not remain charged indefinitely, eventually they will lose their charge.
Symbol which denotes grounding
The ground has an indefinite number of protons and electrons.
Losing or gaining electrons has absolutely no affect on the charge
of the ground. It will remain neutral
Grounding
When you have a build up of negative charge on your body (due to friction), this excess
charge will make its way to the ground by traveling through a conductor
The end result is that all objects
are neutral, and the ground
remains neutral
If the build up of charge on
your hand was positive,
then electrons would travel
up from the ground, through
the door, to neutralize your
hands
p. 477 summary and questions
Charging by Induction
Objects: A charged object and a
neutral object
Action: Objects are brought
close together (touching is not
necessary). Electrons are NOT
transferred, they simply move
within an object.
Outcome: The charged object and neutral object
remain unchanged. There is a temporary build up of
charge on the neutral object.
Van de Graff Generator
http://www.youtube.com/watch?v=7qgM1A3pgkQ
Questions
p. 489 Q: 2, 3,