Definition of Energy (Simple
English Vocabulary Lesson
In this lesson, we share an easy
definition of energy. We will use examples
and pictures to help us understand the different
meanings and uses of this important word.
is the ability to do a physical or mental
activity. The less energy you have, the more tired or exhausted you
are. The more energy you have, the more you feel alert, strong, and
For example, you might say "I don't have the energy
to go running today". This means you feel you don't have enough
"power" (ability, strength) to do physical activity.
Similarly, if you are feeling mentally drained, you
might say "I don't have the energy
to focus on this task".
Here, you are saying you feel you don't have the mental strength
required to complete the task.
- "I don't have the energy to clean the house today. I'm
just too tired."
- "I don't have the energy to go out tonight. I think
I'll just stay home and rest."
- "I don't have the energy to study for this exam. It's
so late at night that I'm unable to focus."
- "I don't have the energy to deal with this problem
right now. Can we talk about it later?"
- "I don't have the energy to play with our dogs today.
I need to take a break."
- "I'm full of energy today. I'm ready to tackle any
task that comes my way!"
- "I'm feeling really energized today. I have the energy
to go for a long hike!"
- "I feel so alive. I have the energy to play with our
dogs and run around the park with them!"
- "You seem especially motivated today. Do you have the energy
to work on this project and see it through to completion?"
is the ability to do work or produce change.
When you lift a heavy object (or any object), you use energy
(apply force to move the object).
When you run or walk, you use energy
(apply force to move your body).
Kinetic energy (the energy of motion): The force of
a moving object.
Energy can take many forms:
Imagine a bowling ball sitting on the floor. The ball is not moving,
so it does not have any kinetic energy.
Now, imagine that you pick up the ball and roll it
down a lane toward a group of pins. As the ball rolls, it gains kinetic
energy because it is moving.
When the ball hits the pins, it transfers some of
its kinetic energy to the pins, causing them to move and fall. The
force of the moving ball to do work, such as knocking down the pins,
is a result of its kinetic energy.
Potential energy (the stored energy of an object):
force an object has because of its position, or the forces acting
upon it. The higher an object is, the more potential power it has.
The more forces acting on an object, the more potential power it
Imagine a book sitting on a shelf. The book has potential energy
because it is being held up by the shelf, and if the book were to
fall, it would hit the floor with force. The higher the book is on
the shelf, the more potential energy
it has because it has a
greater distance to fall.
Or, imagine a rubber band stretched between your feet. The rubber
band has potential energy
because it is being stretched and
held in place. If you let go of the rubber band, it will have the
power to snap back with force into its original shape.
Thermal energy (heat):
the force that an object has due
to the movement of its particles. The faster the particles in an
object move, the more thermal energy
the object has (the
object is hotter).
Imagine a cup of hot tea. The tea has thermal energy
the particles in the tea are moving around and colliding with each
As the tea heats up, the particles in the tea move
faster, increasing the thermal energy of the tea.
When you touch the cup, you can feel the heat being
transferred from the tea to your hand. This is an example of how thermal
energy can be used to do work, such as warming up your hand.
Electrical energy (the energy of electricity):
the force of
electrons moving through a substance (like copper wire). Electrical
can be used to do work, such as powering a light bulb
or a motor.
For example, when you turn on a light switch, the electrons in the
wires are pushed along by a force (electricity
) to power the
light bulb. The electrical energy
produced by the movement
of these electrons is used to do work (illuminate the room).
Chemical energy (the energy stored in
substances): the force that binds atoms together. Chemical
energy is stored inside substances. When these substances are
mixed or changed in some way, the chemical energy is
released. This energy can be used to do work or create change.
For example, when a match is struck, the chemical energy
inside the match is released. This energy creates heat and light
(fire), which can be used to do work (such as lighting a candle).
Solar energy (the energy from the sun):
the force that comes
from our closest star, the Sun. Solar energy
is used to do
work, such as powering a car or providing light and heat to our
For example, when solar panels are exposed to sunlight, they convert
the solar energy
into electrical energy. This electricity
can then be used to do work, such as powering a light bulb or a
Another example is when our bodies are exposed to sunlight, it
produces heat (warms us up).
There are additional kinds of energy, such as
mechanical energy, among others. (Mechanical energy
is the energy an object has due to its movement or position. It is
the total energy of an object that is related to its movement and
how high or low it is. For example, a pendulum has mechanical
energy when it is swinging.)
- "The sun produces a lot of energy, which we can use
to generate electricity."
- "I picked up a heavy box, and it took a lot of energy
to lift it."
- "The car's engine converts gasoline into energy,
which powers the car's movement."
- "The battery stores energy, which can be used to
power a flashlight."
- "Plants use sunlight to convert energy from the sun
into chemical energy."
- "The ball transferred some of its kinetic energy to
the pins, causing them to move and fall."
- "The book had potential energy because it was being
held up by the shelf."
- "The tea had thermal energy because the particles in
the tea were moving around and colliding with each other."
- "The electrical energy produced by the movement of
electrons was used to illuminate the room."
- "When a match is struck, the chemical energy inside
the match is released."
- "Solar panels convert solar energy into electrical
energy, which can then be used to do work."
Hey, how was your workout this morning, Samantha?
It was great! I had so much energy
That's awesome! I wish I had that much energy
in the morning.
Yeah, it really helps to start the day off right.
Do you have any plans for the rest of the day?
Not really. I was thinking of taking it easy and just
relaxing at home.
Well, if you're feeling low on energy
that's a good idea. It's important to listen to your body and give
it the rest it needs.
Yeah, you're right. I'll just take a nap to recharge my
. Otherwise, I won't have enough mental energy for
that task later on.
Good idea. You'll be feeling refreshed and ready to
tackle anything. Have a good rest!
Hey, I heard you have been working on improving
efficiency of car engines. How's it going?
It's going well! We've been testing different
designs and materials to see which ones can optimize the energy
conversion in the engine.
That's interesting. What kind of energy
conversion are you looking at?
We're mainly focused on improving the efficiency
of the internal combustion process. That's where the energy
from the fuel is converted into mechanical energy
I see. And have you made any progress?
Yeah, we've made some good strides. We've been
able to increase the energy
conversion efficiency by about
5% by using a new type of fuel injection system.
That's great! Any increase in energy
efficiency is always a positive step.
Definitely. We're always looking for ways to
reduce the amount of energy
wasted in the process and make
the most of the resources we have.
So, what's next on your list of improvements?
We're planning on experimenting with different
types of fuels to see if we can find one that has a higher energy
density and burns more efficiently.
That's a good idea. Higher energy density means
can be stored in a smaller space, right?
Exactly. And a more efficient burn means less energy
is lost as heat and more of it is converted into usable mechanical
It sounds like you're making some significant
progress in optimizing the energy
conversion in car engines.
Yeah, we're definitely making progress. But
there's always more to be done. There are always new technologies
and materials to explore, and there's always room for improvement.
I agree. It's important to keep pushing the
boundaries and finding new ways to increase energy