20.1 Electric Charge and Static Electricity
Chapter 20
Electricity
Lightning provides a
powerful display of
electrical energy.
20.1 Electric Charge and Static Electricity
20.1 Key Concepts
• What produces a net electric charge?
•
What determines whether an electric force is
attractive or repulsive?
•
What determines the strength of an electric
field?
•
What are three ways in which charge is
transferred?
•
How does a static discharge occur?
20.1 Electric Charge and Static Electricity
When you take clothes out of a
dryer, some of them can
____________
together.
stick
If you pull the clothes apart in a
darkened room, you can see
___________
that are like tiny
sparks
bolts of lightning
Lightning and “static cling” have
similar causes – the movement
of _________________
electric charges
20.1 Electric Charge and Static Electricity
Electric Charge
Recall that electric charge is a property that
attract
causes subatomic particles to ____________
or
_____________
one another.
repel
negative
Electrons have _________
charges and protons have
____________
charges
positive
20.1 Electric Charge and Static Electricity
Electric Charge
How many protons does this atom have?
8
And electrons?
8
neutral
This atom is ___________
equal
because it has an ________
number of positive and
negative charges
20.1 Electric Charge and Static Electricity
Electric Charge
• If an atom gains electrons (e-), it becomes
a ______________
charged ion.
negatively
• If an atom loses electrons (e-), it becomes
positively
a ______________
charged ion.
• An excess or shortage of electrons
produces a _______
electric charge.
net
20.1 Electric Charge and Static Electricity
Electric Charge
coulomb (C).
The SI unit of electric charge is the __________
6.24 x 1018
• It takes about __________________
electrons to
produce a single coulomb.
10 to 20 coulombs of
• A lightning bolt is about ____________
0.025 coulombs.
charge, and a camera flash is about _______
20.1 Electric Charge and Static Electricity
Electric Forces
Recall that like charges ____________,
and
repel
attract
opposite charges _____________.
The force of attraction or repulsion between
electrically charged objects is _____________
electric
___________.
force
20.1 Electric Charge and Static Electricity
Electric Forces
Doubling the net charge on one object
doubles
____________
the electric force.
Electric force and
net charge have a
_____________
directly
proportional
relationship
20.1 Electric Charge and Static Electricity
Electric Forces
Doubling the ____________
between the
distance
reduces
objects _______________
the electric force to
one fourth the original force.
Electric force and
distance have an
inversely
_____________
proportional
relationship
20.1 Electric Charge and Static Electricity
Electric Forces
Inside an atom, electric forces are much
stronger
________________
than gravitational forces.
• form chemical bonds
Electric forces also cause
_______________
and
friction
other contact forces
20.1 Electric Charge and Static Electricity
Electric Fields
The effect an electric charge has on other
charges in the space around it is the charge’s
electric _________________.
field
• .
Field of a positive charge
Field of a negative charge
20.1 Electric Charge and Static Electricity
Electric Fields
The strength of an electric field depends on…
amount
• the ______________
of charge that produces
the field
distance
• and on the ______________
from the charge.
20.1 Electric Charge and Static Electricity
Static Electricity and Charging
Static electricity is the study of the
_________________
of electric charges.
behavior
Charge can be transferred by…
friction
__________________
contact
__________________
__________________
induction
20.1 Electric Charge and Static Electricity
Static Electricity and Charging
When studying charge transfers, keep in mind
the law of conservation of charge…
• states that the total charge in an isolated
constant
system is _______________.
• when there is a charge transfer, the total
same
charge is the ____________
before and after
the transfer occurs.
20.1 Electric Charge and Static Electricity
Charging by Friction
Rubbing a balloon on your hair causes charging by
friction.
hair
• Electrons move from your ____________
to the
balloon
_________________
because atoms in rubber have a
greater attraction for electrons than atoms in hair.
• The balloon picks up a net
negative
_____________
charge.
• Your hair loses electrons and
positively
becomes ________________
charged.
20.1 Electric Charge and Static Electricity
Static Electricity and Charging
Charging by Contact
A ________________
generator builds a charge on a
Van de Graaff
metal sphere.
Touching the sphere
transfers charge by contact.
The sphere is still charged,
but its net charge is
____________________
reduced
20.1 Electric Charge and Static Electricity
Charging by Induction
Walking on a carpet builds a ________________
charge on
negative
your body.
The negative charge in your hand
repels electrons in a metal
doorknob
Describe the movement of the
electrons in the doorknob as
the hand approaches.
They move away from the hand
20.1 Electric Charge and Static Electricity
Charging by Induction
The doorknob is still _____________,
but charge
neutral
has moved ______________
it.
within
This is induction,
a transfer of charge
_____________
without
contact between
materials.
20.1 Electric Charge and Static Electricity
Static Discharge
Static discharge occurs when a _____________
pathway
through which charges can move forms
________________.
quickly
Why do you get a shock from a
doorknob?
__________
becomes charged when
Air
the gap between your finger and the
doorknob is _________.
small
This air provides a path for
_______________
to flow.
electrons
If the room is dark, you can
even see the spark.
20.1 Electric Charge and Static Electricity
Lightning is a more ______________
discharge.
dramatic
• Charge can build up in a storm cloud
from _________________
between
friction
moving air masses.
• Negative charge in the lower part of
the cloud induces a positive charge
in the _____________
below.
ground
air
• Eventually the ________
between
becomes charged, forming a
_________________
for electrons
pathway
to travel from the cloud to the ground.
20.1 Electric Charge and Static Electricity
Assessment Questions
1. Which of the following would double the electric
force between two charged objects?
a.
b.
c.
d.
doubling the mass of the objects
cutting the net charge of both objects in half
doubling the net charge of one of the objects
cutting the distance between the objects in half
20.1 Electric Charge and Static Electricity
Assessment Questions
2. The attractive or repulsive effect an electric
charge has on other charges in the space around
it is the charge’s
a.
b.
c.
d.
electric force.
electric field.
static electricity.
static discharge.
20.1 Electric Charge and Static Electricity
Assessment Questions
3. An object becomes charged by induction when
there is a
a.
b.
c.
d.
transfer of electrons, as the object rubs against another object.
transfer of charge, as it contacts another charged object.
transfer of charge by motion of electrons within the object.
a sudden movement of electric charge from another object.