Energy, Power, and Electricity
Subject Area(s)
number & operations, physical science, science and technology
Associated Unit
Clean Energy
Lesson Title
Introduction to Energy, Power, and Electricity
Grade Level
11 (9-12)
Lesson #
2 of 5
Lesson Dependency
None
Time Required
140 minutes including associated activities
Summary
Students learn about the concepts of energy and power, how they differ, and how they relate to
electricity. Additionally, students learn about magnetism and its relationship to electricity in
electromagnets, generators, and motors.
Engineering Connection
Energy and power are some of the most basic concepts in engineering design and analysis.
Almost every engineered product will consume, dissipate, or necessitate energy/power in its
function or manufacturing processes. Mechanical engineers may be concerned with power
generation from an internal combustion motor, civil engineers must take heat power absorption
and dissipation into consideration when constructing structures, and electrical engineers must be
aware of how circuits consume electrical power and how that power consumption/heat is
dissipated.
Electricity is a ubiquitous component of every form of engineering. Engineers create
electricity with generators and use it with lights, computers, appliances, and motors. The
efficient creation and consumption of electricity is of utmost importance to mitigating climate
change.
Engineering Category
Page 1 of 7
Relates science concept to engineering
Keywords
clean, energy, power, atom, electron, voltage, current, resistance, Ohm’s Law
Educational Standards
Colorado State Science: Colorado, 2011, science, physical science, grades 9-12, 5a: Use direct
and indirect evidence to develop predictions of the types of energy associated with objects
Colorado, 2011, science, physical science, grades 9-12, 5b: Use appropriate measurements,
equations and graphs to gather, analyze, and interpret data on the quantity of energy in a system
or an object
Colorado, 2011, science, physical science, grades 9-12, 6c. Describe energy transformations
both quantitatively and qualitatively
Colorado State Math: NA
ITEEA: ITEEA, Standard 4, Grades 9-12, I. Making decisions about the use of technology
involves weighing the trade-offs between the positive and negative effects.
Pre-Requisite Knowledge
Basic understanding of the components and structure of atoms. Basic understanding of algebra,
variables, and solving single linear equations.
Learning Objectives
After this lesson, students should be able to:
 Explain what energy is
 Describe several sources of energy
 Describe what power is and how it differs from energy
 Distinguish between an energy requirement and a power requirement
 Explain qualitatively what voltage, current, and resistance are
 Solve Ohm’s Law as it relates to electrical power
 Solve for an energy requirement given a power and time
 Build and explain the physics behind an electromagnet
 Build and explain the physics behind a homopolar motor
Introduction / Motivation
[Have the attached PowerPoint ready to go. Play the cheesy School House Rock video about
electricity]
What is electricity? How does electricity relate to energy? If there is such a thing as clean
energy, is there such thing as clean electricity? Electricity is one of the fundamental tools of all
21st century engineers. All engineers need to know how electricity works and how it relates to
the problems they are trying to solve.
However, electricity does not exist alone. Electricity has a companion, magnetism, that is
inextricably linked to electricity. The interplay between electricity and magnetism is very
fascinating, and you will shortly learn how to do amazing things with these two tools. We can
generate electricity using a spinning shaft, or we can make a shaft spin using electricity!
The critical importance of an understand of energy, power, and electricity and how they
interplay cannot be understated!
Lesson Background & Concepts for Teachers
Energy: energy is one of the most important concepts in engineering. Energy is the capacity of
some system to do work. Energy can exist in many different forms such as

Kinetic energy: a ball moving, or the wind blowing

Thermal: a hot oven or coal fire

Chemical: a stick of dynamite or food

Electrical: the energy that comes through our household outlets

Nuclear: a nuclear bomb or reactor
Energy cannot be created or destroyed, it can only change forms. In fact, energy can even
change into matter or vice versa (E=mc^2). Many units can be used to describe an amount of
energy, but the most common are joules (SI), calories (food), and kWh (electricity bill).
It can be very difficult for students to understand energy because, unlike power, it is difficult to
experience. Vast quantities of energy can be consumed or “created” over very long periods of
time, but in a human experience it can be very difficult to comprehend how much energy is
changing forms. Take for example a mountain. A mountain takes an immense amount of energy
to form, but that formation occurs over millions of years, so we do not typically think of
mountains as containing a lot of energy. A volcano of the same height as the mountain can form
in much less time and in a much more dramatic (read: fast) fashion, leading the layperson to
think that volcanoes take more energy to make than a mountain. In reality the mountain and the
volcano (assuming they are the same size/shape) took roughly the same amount of energy to
make.
Power: power is a way of measuring how much energy is being produced/used in a given time
and can be described by the equation P = E/t where P is power, E is energy, and t is time.
Therefore, the less time it takes to deliver a given amount of energy, the more power will be
generated/used. Take the mountain/volcano example again. The mountain may take millions of
years to form, whereas the volcano may take a fraction of the time. Therefore, the volcano’s
creation took far more power than the mountain’s. They both took equal amounts of energy, but
the volcano was created much faster.
Another way students may find visualizing energy/power easier is by thinking about the human
body. A strong person and a weak person are both told to move a cinder block to the top of a
wall. The strong person decides to throw the block to the top of the wall while the weak person
decides to slowly push it up a gently sloping (frictionless) ramp. Both people eventually get the
brick to the top of the wall. In the end both bricks are at the same height, and they both have the
same potential gravitational energy. However, the strong person got the brick there faster, and
therefore needed more power than the weak person.
Power is a much more tangible idea than energy for most students. Power can be “felt” while
energy cannot. Power can feel like acceleration, heat dissipation, electrical shock, or water
pounding down from a waterfall. When energy is delivered (over a certain amount of time) we
call it power.
Electricity: because electricity is (or is in some areas becoming) the most common form of
energy transfer, this unit and lesson will deal primarily with electrical energy and power.
Atoms are made up of two structures: a nucleus and an electron cloud. The nucleus contains
protons and neutrons while the electron cloud contains electrons. When there is a bias (voltage)
for electrons to move one way or another, and if the atoms are good at sharing electrons (like
metal), electrons will transfer from one atom to another. This is electricity; is the transfer of
electrons from one atom to another.
The simple parameters that define an electrical circuit are voltage, current, and resistance.
These can be very difficult for students to understand, but an analogy to a river is often helpful.
 Voltage is the bias or “pressure” pushing electrons from one atom to another. Voltage is
measured in volts. This can be thought of as the slope that a river is on. The steeper
the river bed, the more bias the water was to flow downhill. It does not matter how
much or how little water there is, if a hill is steep it will really want to flow down
quickly, and if a hill is not very steep the water will flow slowly.
 Current is the quantity of electrons moving past a plane per unit of time. Current is
measured in amps. This can be thought of as the width/depth/speed of a river. If a
river is deep, wide, and fast, it is moving a lot of water. The more water, the more
current. To vocabulary even lines up!
 Resistance is a measure of how “difficult” it is for electrons to change from one atom to
another. Resistance is measured in ohms. This is primarily a function of the material
the electricity is flowing through and the cross section of that material. You can think
of resistance the number of rocks/debris in a river. The more stuff that is getting in the
way of the water’s forward progress, the slower it will move. This is somewhat
analogous to electrical resistance.
Electrical power is the product of voltage and current (P=VI). This is intuitive if we think of
the power in a river. A creek that is very steep/fast, but does not have very much flow is not
very powerful. Similarly a river that is very deep/wide, but slow moving and flat is also not
terribly powerful. However, a steep whitewater river with lots of flow is indeed powerful.
Ohm’s Law: Ohm’s Law describes the relationship between voltage current and resistance as
takes the form (V=IR). Given two of the three variables, the unknown can be solved for.
Why electrical power is transmitted at high voltage?: Resistive losses in an electrical circuit
are found by the equation Plost=I2R. Hence, it is critical that current be limited; if current is
reduced 10 times, power loss is reduced 100 times. We can maintain the same power in the lines
by increasing the voltage proportionally to the current decrease. This is the primary reason
power is transmitted at high voltage.
Ohm Zone: Ohm is a simple game where batteries, resistors, switches, light bulbs, and
voltage/current meters can be assembled. This tool is useful for demonstrating to students how
current/voltage change depending on how many components are added to a system. The
software (Adobe Shockwave driven) can be found at www.article19.com/shockwave/oz.htm.
Electromagnets: Any current-carrying wire will create a magnetic field around its
circumference. This magnetic field, whose strength is governed by Ampere's Law, wraps around
the wire and its strength (for an infinitely long wire) is governed by Ampere's Law: B=μ0I/(2πr)
where μ0 is the magnetic permeability of free space. If this wire is then bent into a coil, then all
components of each segment of wire's magnetic fields will cancel except the components that
point down the axis of the coil and down the outside of the coil. Thus, by wrapping wire into a
coil and running current through it, we are able to generate a powerful magnetic field down the
axis of the coil. This coil of wire is often called a solenoid. The strength of this field can be
greatly increased by placing an object inside the coil that has high magnetic permeability. Since
B=μ0I/(2πr), a high permeability compared to free space can significantly increase the strength of
the magnetic field. Most ferrous (iron) materials have a magnetic permeability ~1000X that of
free space. This is why most electromagnets have an iron core.
Homopolar Motors: A homopolar motor is a special kind of motor that only requires a single
magnet. Additionally, the direction of poles on the magnet do not change relative to the axis of
rotation of the motor. A homopolar motor works by using the Lorentz force of a magnetic field
on a moving electrical charge to "push" a wire through a magnetic field. Referring to
illustrations in the presentation associated with the Introduction to Energy, Power, and Electricity
lesson, one can see that as current moves through the wire, the charged particles' direction is
orthogonal to the direction of the magnetic field. Thus, a force (the so-called Lorentz Force) is
felt by the moving charge (inside the wire) in the direction that is orthogonal to the direction of
the current and the magnetic field (according to the right hand rule):
.
In order to use the right hand rule, point your finger of your right hand in the direction of the
current, then curl your fingers towards the direction of the magnetic field. Your thumb will point
in the direction of the force.
So, a homopolar motor works by taking advantage of the Lorentz force to "push" the wire
around the battery.
Vocabulary / Definitions
Word
Definition
energy
Energy is the capacity of a system to do work. Energy is typically
measured in joules, calories, or kWh (kilowatt-hours)
power
Power is a quantity that describes how much energy is being
harnessed/used in a given time period. Power is typically measured in
watts or horsepower.
electricity
Electricity is the transfer of electrons from one atom to another.
voltage
Voltage is the “pressure” that biases electrons to move (create
electricity). Voltage is measured in volts.
current
Current is the quantity of electrons passing through a plane per unit
time. Current is measured in amps (Coulomb/second).
resistance
Resistance is a quality of a conductor that resists the movement of
electrons. Resistance is measured in Ohms.
Ohm’s Law
Ohm’s Law is the equation V=IR and relates voltage, current, and
electromagnet
generator
motor
homopolar motor
resistance in simple circuits.
An electromagnet is a simple device uses the flow of electricity
through a coil to generate a magnetic field.
A generator uses mechanical energy to make electricity.
A motor uses electricity to make mechanical energy.
A homopolar motor is a special kind of motor that only requires a
single magnet. Additionally, the direction of poles on the magnet do
not change relative to the axis of rotation of the motor.
Associated Activities
Electromagnets and Homopolar Motors Activity
Lesson Closure
Energy and power are two closely related topics that describe the ability of a system to do
work. Power differs from energy because power includes how much time it takes to expend or
collect a certain amount of energy and it is usually what we are really thinking about when we
say the word “energy.” Electricity is the primary way that our society transfers energy from one
location to another. We can understand the relationships between the three primary variables in
electricity, voltage, current, and resistance, using Ohm’s Law.
With an understand of energy, power, magnetism, and electricity, engineers can start to build
electromechanical devices that consume electricity to make mechanical power, or use
mechanical power to make electricity. As young engineers, you are starting to learn the skills
you need to wield the power of the laws of physics to make useful products and solutions for
people and the planet.
Assessment
Pres-Lesson Assessment: Ask students to discuss the following questions in small groups and
present their answer on one question to the class:
 What is energy and how is it different from power?
 What are 10 examples of things you deal with in your life that take energy or power?
 What is electricity? Can you explain how it works?
 What are 10 examples of things in your life that need electricity?
Post-Introduction Assessment: none
Lesson Summary Assessment: Break students into groups of 3-4. Ask them to brainstorm three
different methods of how electrical power is currently generated. Given this, ask students to
image one additional way that electrical power could be generated/converted from another
energy source. Have students present this idea to the class by answering the following questions:
 Where does your electricity generator take energy from?
 Is your electricity generator clean?
 Do you think your electricity generator is realistic/affordable?
Self Assessment: Students will fill out the “Energy, Power, and Electricity” skeleton notes and
worksheet.
Homework: None suggested
Lesson Extension Activities
None
Additional Multimedia Support
Ohm Zone: http://www.article19.com/shockwave/oz.htm
References
None
Attachments
Energy, Power, and Electricity Presentation (ppt)
Energy, Power, and Electricity Presentation (pdf)
Energy, Power, and Electricity Skeleton Notes and Worksheet (doc)
Energy, Power, and Electricity Skeleton Notes and Worksheet (pdf)
Electromagnets and Homopolar Motors Activity (doc)
Electromagnets and Homopolar Motors Activity (pdf)
Energy, Power, and Electricity Image, Figure, & Table Description (doc)
Energy, Power, and Electricity Image, Figure, & Table Description (pdf)
Energy, Power, and Electricity Summary (doc)
Energy, Power, and Electricity Summary (pdf)
Other
None
Redirect URL
None
Contributors
Daniel Wilson B.S. Licensed Educator, Michael De Miranda Ph.D., Thomas Siller Ph.D., Todd
Fantz Ph.D.
Copyright
Copyright © 2010 Colorado State University.
Supporting Program
Engineering and Technology Education Program, College of Education & College of
Engineering, Colorado State University. This content was developed by the Engineering and
Technology Education Program under National Science Foundation GK-12 grant no.
GDE0841259.