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Electricity
Electric Charge and Force

Electric Charge- electrical property of matter
that creates a force between objects.
Charges- 2 charges generated by a build-up of electrical
charge: positive (+) and negative (-).
Like charges repel and opposite charges attract.
Net charge- The total amount (sum) of
charge on an object.
 When the + and – charges are equal, there is
no net charge. Whenever there is an
imbalance in the # of + & e-, you have a net
electrical charge.
 The difference in the number of + & e- is the
electrical charge value. + charged objects
have more protons, - charged objects have
more e-.
The Coulomb, C- the SI unit for
electrical charge is the coulomb
(1.6 x 10-19). e- & + have
exactly the same amount of
charge:
+ =1.6 x 10-19
e- = -1.6 x 10-19

Because the amount of charge on
an object depends on the # of + &
e-, the net charge of a charged
object is ALWAYS multiplied by
1.6 x 10-19 C

Conductors & Insulators


Conductors always allow charge to
flow.
Insulators restrict or limit the flow.
Objects can be charged by the
transfer of e-s. Electrons transfer
easily from one atom to another,
thus they can transfer from one
material to another. This can occur
with or without friction (rubbing).
Think of rubbing a balloon on your head,
then getting a balloon to stick to the wall.

Electric Force- force generated by the
repulsion/ attraction between two or more
charged objects. It also holds atoms
together and other molecules. Without
it… life would be impossible.

Electrical force depends on charge and
distance of objects. The more charge each
object has the stronger the electrical force.
The further away the objects are, the weaker
the electrical force becomes.
 Electrical force acts through a
field. An electric field is
generated around a charged
object due to its charge.
(electric field lines leave + charged particles
e.f.l. are attracted to – charged particles.)
 E. F. L.- point in the direction
of the electric force and help
define the electric field.
ELECTRIC FIELD LINES
NEVER CROSS! Positive
electric field lines repel each
other. The # of field lines
reflects/indicates strength of
charge.
Current
 Voltage and Current
 A. Electrical potential energy: Potential energy
of a charged object due to its position in an
electrical field.
 Potential difference: is the charge of the
electrical potential energy per unit of time.
 occurs as a charge moves from one
place to another in an electrical field.
Voltage -SI units for potential difference
measure in volts, V -equal to one joule
per coulomb (1J/C).
 voltage exists across the terminals of a
battery (1.5 V to 12 V). These batteries
are called cells.
 Current - the rate that electric charges
move through a conductor.
 Electrical Resistance
 A. Resistance: the ratio of the voltage
across a conductor to the current it carries.
In other words how much electric power
can it carry?
 Resistance formula:
 Resistance = voltage/current or R= V/I.
 Units ohm Ω
 B. Conductors have low resistances.
 C. A resistor is an insulator, any material or
solution that does not allow the flow of
electrons. In other words they have high
resistance
 Circuit symbols and Circuit diagrams