What is an electric
charge?
An electric charge is
the electrical
property of matter
that creates a force
between objects.
•
the attracting or
repelling
behavior of a
material.
What is an electric
charge?
To create this
charge,
electrons
must move
from one
atom to
another.
What is an electric
charge?
All matter is made up
of atoms
Atoms are made up
of smaller
particles called
protons, neutrons
and electrons.
Why do objects become charged?
 An
imbalance of
its protons and
electrons occurs
 Protons
positive
 Neutrons neutral
 Electrons
negative
Conservation of Charge
Electrons are bound
more tightly to
some atoms and
molecules than
others. When an
electron is
transferred, it
creates an ion.
Conservation of Charge
A charged atom is an ion.

positive ion – atom
loses electrons

negative ion – atom
gains electrons
Charge is always
conserved – never
created or destroyed!
ELECTRICAL CONDUCTORS
Conductors allow
electrons to flow
 Conductivity depends
upon how tightly the
atom holds on to its
electrons.
 loose electrons in a
material conduct the
electric charge through
(metals).
Examples of conductors:
Metal, graphite, etc.

ELECTRICAL CONDUCTORS
In solid conductors, the
electrons carry the charge
through the circuit because
they are loosely held.
In fluids, like those in a car
battery, positive and negative
ions and electrons may
compose the flow of electric
charge.
ELECTRICAL INSULATORS
Insulators DO NOT conduct
electricity well!! They provide
RESISTANCE to the flow of
electrons.
RESISTANCE IS CAUSED BY
INTERNAL FRICTION
Examples of Insulators: Glass,
wood, rubber, etc.
SEMICONDUCTORS
Semiconductor –
material made to
behave sometimes
as insulators and
sometimes as
conductors
(germanium and
silicon).
How can objects become
charged?
Charging by Contact –
1) Two objects are rubbed
against each other and
electrons are transferred.
PROTONS NEVER
MOVE from one atom
to another.
How can objects become
charged?
2)
A charged object touches a neutral
object, transferring electrons –
PROTONS NEVER MOVE from
one atom to another
How can objects become
charged?
Charging by Induction
(charging at a
distance) – A
charged object is
held near a neutral
object and causes an
overall charge.
Charge Polarization
When charges rearrange in an
atom, one side becomes
slightly more positive and
the other side becomes
slightly more negative. The
atom is electrically
polarized. Ex – charged
comb attracting bits of
paper or charged balloon
sticking to the wall.
Electric Fields
An electric field surrounds
every electric charge and
exerts the force that causes
other electric charges to be
repelled or attracted.
Electric fields are represented
by arrows that show how
the electric field would
make a positive charge
move.
Charges Exert Forces
Unlike charges attract
each other
(positive and
negative)
Like charges repel
each other
(positive to
positive or
negative to
negative)
Charges Exert Forces
Just like gravity, the
amount of
electrical force
exerted on an
object is related to
the following:
1. Distance from the
charged object
2. Strength of the
charge on the
charged object
What is an electric
charge?
Protons are positive and are
found in the nucleus of the
atom
Neutrons are neutral and found
in the nucleus of the atom
Electrons are negative and are
found in regions around the
outer edges of the atom