Intro to Electricity
Knowledge: Big Ideas
Electrons are the only subatomic particle that is able to move in a substance (other than
the entire atom moving). Materials can build up an abundance of electrons and have a net
negative charge. Electrons can also leave an object and that object will have a net positive
charge. Electrons will always attempt to repel each other and therefore will try to move from
areas of negative charge to areas of positive charge. When you rub your feet on carpet and build
up an excess of negative charge and you touch a door knob or other object, the charge will leave
your body and go to that object. Doing this creates a spark. Voltage is he potential difference
between areas of high charges and areas of low charges. Electric charges will want to move
from areas of high voltage to areas of low voltage.
“A Van de Graaff generator is an electrostatic machine which uses a moving belt to
accumulate very high voltages on a hollow metal globe. The potential differences achieved in
modern Van de Graaff generators can reach 5 megavolts. Applications for these high voltage
generators include driving X-ray tubes, accelerating electrons to sterilize food and process
materials, and accelerating protons for nuclear physics experiments. The Van de Graaff generator
can be thought of as a constant-current source connected in parallel with a capacitor and a very
large electrical resistance.” (http://en.wikipedia.org/wiki/Van_de_Graaff_generator)
Electrostatic induction can be used to induce charge in an uncharged object. When a charged
object comes into proximity of another object, it will induce the opposite charge on the other
object closest to the charged object. The positive charges do not move! Only the negative
charges (electrons) move. Lightning is caused when there is a charge separation between a cloud
and the ground. The lightning bolt is seen when the charges discharge and the electrons in the
lightning neutralize the charge separation. This could be from cloud to ground, cloud to cloud
and sometimes ground to cloud. Electricity always wants to flow to the ground. The Earth is
considered an infinite source of electric charges and since the charge always wants to flow from
high to low voltage, charge will want to flow to the ground.
Conductors are materials that allow the flow of electrons to pass freely through them. They
have loosely held valance electrons and therefore allow free electrons to pass through them.
Metals are good examples of conductors. Insulators do not allow free electrons to pass through
them. They have very tightly held valence electrons. Examples are rubber, plastic, wood, glass,
etc. Conductors can have different amounts of electrical resistance. Although electrons can
move through them, some materials resist the flow of electrons more than others. The flow is
resisted by the free electrons colliding with atoms and other electrons in that material. These
collisions can create heat and light (energy transformation). Good examples are a lightbulb,
electric stove burner and a toaster.
Knowledge: Experiences, Patterns, and Explanations
Initial
Student
EPE
Observations or
experiences (examples,
phenomena, data)
Patterns (laws,
generalizations, graphs,
tables, categories)
Explanations (models,
theories)
Rubbing objects together.
Getting a shock from touching
an object (doorknob).
Clothing sticks together when
you take it out of a dryer.
Lightning strikes that can burn
trees or harm/kill humans.
Wires are made of copper with
rubber or plastic coating.
A light bulb gets hot when it’s
on for a while.
An electric stove burner gets red
and hot from electricity (or a
toaster).
You are safe from lightning in a
car because there is rubber
between you and the ground.
There are both positive and
negative electric charges.
When objects rub together,
they can build up a charge.
Opposite charges attract each
other and like charges repel
each other.
When something is charged
and it draws near an object
that is neutral, the charge will
move from the charged object
to the uncharged object.
(getting shocked from a
doorknob)
Electricity can flow through a
conductor. An insulator will
resist the flow of electricity.
Electricity is energy that can
move, we can see it in
lightning, and we use it to
power certain devices. It
can harm you if you are
electrocuted
When you rub objects
together, electrons may move
from one object to another
causing an unbalanced charge.
Opposite charges attract each
other and like charges repel
each other.
When something is charged
and it draws near an object
that is neutral, the charge will
move from the charged object
to the uncharged object.
Electric current is allowed to
pass through a conductor but
not an insulator (wire with
copper surrounded by plastic).
When you hold your hand near
the generator the charge will
jump from the charged dome
to your neutral body (high
voltage to low) in an attempt
to reach the ground.
When you stand on an
insulator, the charges from the
generator can build up on your
body causing your hair to
stand up. If someone standing
on the ground touches you, all
Electricity results from
electric charges in
subatomic particles.
Static electricity is caused
from charges that build up
on an object (not moving)
Electric current is the
movement of these electric
charges. It can be used to
power electronic devices.
Conductors allow current to
pass through them. They
have relatively low
resistance. Some materials
are better conductors than
others (varying degrees of
resistance)
Insulators have such high
resistance that they do not
allow electric current to pass
through it.
The more resistance a
material has, the more it will
impede electric current. If
current passes through an
object with higher resistance
it will generate a lot of heat
(electrical friction)
Goal EPE Rubbing a balloon on your head
causes charge to build up on the
balloon.
Getting a shock from touching
an object (doorknob).
Clothing sticks together when
you take it out of a dryer.
Lightning strikes that can burn
trees or harm/kill humans.
Wires are made of copper with
rubber or plastic coating.
A light bulb gets hot when it’s
on for a while.
An electric stove burner gets red
and hot from electricity (or a
toaster).
You are safe from lightning in a
car because there is rubber
between you and the ground.
There are both positive and
negative electric charges.
the charge built up on you will
travel through that person to
the ground.
Objects charged (on the dome)
will repel each other since
they are both negatively
charged.
Application: Model-based Reasoning
Inquiry: Finding and Explaining Patterns in Experience
Possible Objectives for Student Learning
Objective
Michigan Objective(s): HSCE or GLCE
Type
1. P.PM.04.18 Identify objects that conduct heat and electricity. (4th
grade)
Identifying
P3.7x Electric Charges — Interactions
Charged objects can attract electrically neutral objects by induction.
P3.7c Draw the redistribution of electric charges on a neutral object when a
charged object is brought near.
P3.7d Identify examples of induced static charges.
P3.7e Explain why an attractive force results from bringing a charged object
near a neutral object.
P4.10D Discriminate between voltage, resistance, and current as they apply to
an electric circuit.
Identifying
Using
Specific Lesson Objective(s)
1. Predict how objects are charged by movement of “free” electrons both by conduction and
induction.
2. Predict how charged objects behave when placed near or in contact with other objects
3. Explain the phenomena of lightning using ideas of charged objects.
4. Use the concept of voltage to explain why and how charges will move.
5. Use the concept of voltage to make predictions of how charges will effect objects using
the Van Der Graaff generator
6. Use the concepts of conductors and insulators to explain how current will travel through
certain materials and generate heat
7. Use concept of resistance to predict whether a material will conduct or insulate. Use this
to explain why certain materials heat up and emit light when current is passed through it.
Using
Using
Using
Using
Using
Using