Today we're going to be continuing on our energy conversion.
And we're going to dive a little deeper into the first law of energy conversion
that I covered very briefly in the last lecture.
And show some examples and try to get a little better understanding of what we're
talking about and what the, what the limitations do to us regarding the first
law of energy conversion. That say's you cannot create or destroy
energy. and we're dealing with the middle box
here, where we're, converting energy from one form that we find in it's natural
state, to the form that society Needs and wants they're willing to pay for.
We've already been over this diagram, looking at all the infrastructure that we
have in order to carry out this conversion process.
And repeating the 1st law, total energy cannot be created or destroyed, it is the
1st law and That, that sometimes comes a little surprising, because a lot of times
in the press, and the media, and the public, we talk about producing energy.
but when we produce energy, we're always using energy on the other side somewhere.
There's got to be an energy input before we can produce it from our hot air
furnace or from our, with our automobile or for our wind turbine or something.
There's got to be an energy source in order to produce energy.
So we're not, we're never creating energy, we're only converting it again
from one form to the other. So I can't say that enough.
Now there, to dive a little deeper we need to understand what types and forms
of energy we're talking about here. What all, are some of the different forms
that we typically deal with. Well work is one of the, one of the most
valuable forms that we have and that is, as an example, is a turning shaft that
turns the axle to our car with a torque on it that drives our car or when we
pedal our bicycle, we're turning a shaft that powers the rear wheel that pushes us
up a hill or against the wind resistance as we ride our bicycle electricity is
another form of energy. And there of course, that's a current and
voltage that's carried over a wire. Electricity is a very nice form of
energy. Because it's one that can be transported
over long distances very efficiently. Work, you got to have a shaft.
And to carry that work from one place to another.
Of course, you don't want to have a mile off shaft to carry work from one place to
another. But we can produce electricity at one
place and carry it over a mile long power line.
And then use it to power an electric motor on the other end.
And that can produce our work. So electricity is one that.
That is a very nice form of energy. But, of course, we don't find it in a
natural state. We always have to generate it from some
other source. Kinetic energy is one that we're
probably, fairly familiar with in, that regarding a moving car.
you have to put energy into the car from when you're at a stop light in order to
accelerate it to 25 mph to get to the next stop light in, in traffic.
so it has kinetic energy and then if, unless you're dealing with a hybrid car,
you put your brakes on which produces friction and turns that kinetic energy
into heat. That heats up the breaks and dissipate
that energy, that kinetic energy. Dissipate it into thermal energy or into
the atmosphere. So it's wasted, so to speak.
we put it into the card to create the kinetic energy but then we don't get it
back out. The hybrid car uses a generator to.
link into the brakes, and the braking is done with a generator that generates
electricity then and stores it in the battery to accelerate when we get ready
to start back up, from the stop light. thermal energy is and, and that's
sometimes we call heat. This one that a warm cup of coffee is
contains thermal energy. Any kind of, of object that has a
temperature above ambient temperature. Whatever the ambient atmospheric
temperature is at that point in time. If you have any substance at a
temperature higher than that, that's what we call thermal energy or heat.
Hot air, hot coffee, or warm house inside.
All that's thermal energy. And it's another form of energy that we
want and like. Hot water to shower with is another place
where we have thermal energy or heat, as sometimes we call it.
chemical energy is one that's in the, the chemical make up with our, our electrons
bonded to the other molecules into the nucleus of our atoms and molecules and,
we can carry out a chemical reaction and release that, chemical energy, or we can
create more chemical energy by putting energy into it driving the chemical
reaction to increase the chemical energy. So gasoline is 1 that is an example
there. Gasoline has chemical energy in it.
And we carry out a chemical reaction of that gasoline with oxygen in the air.
As we saw the formula when we Talking about oil and, that releases, that
chemical energy as thermal energy, or heat and can, and produces a very high
temperature flame, that when can use to heat homes or to heat hot water or Drive
a power plant. Radiation is the final example that I
give you and that's of course the best example is the sun's rays that, radiation
coming from the sun is radiation energy. You also feel it in front of a fireplace,
if you have a. Wood burning fireplace then, and you have
a lot of hot coals. Those coals radiate that, and that's
thermal radiation we call it. But the sun rays of course, that
radiation is 1 that we use in solar energy to produce electricity or produce
hot water to heat our pools and. The things, so those are just some of the
forms of energy and we can convert these forms from one to the other, as is shown
here. So we put energy into some kind of energy
conversion system that would design to take that form of energy.
Work, electricity, heat, chemical energy kinetic energy, potential energy, etc.,
and, and convert it to some other form of work, eletric, that is one of the work,
electricity, heat, chemical, kinetic, potential, etc.
for instance, you can take you can take work, and put it into a generator,
electric generator and electricity comes out of the generator.
So that's one of the energy conversion processes.
That we do a lot in, to produce electricity.
we might put heat in by burning coal in a power plant, and dry, and boil steam and
go through a cycle that produces electricity also kinetic energy is I
already mentioned, an automobile is one of the best examples of that.
Potential energy, if the automobile is high on a mountain then it has potential
energy. As it, and gives up that potential energy
as it comes down the mountain or comes down the hill and you can Easily convert
kinetic energy from the dropping potential energy as you coast down the
hill with a bicycle or a car. So we got potential energy coming in on
the left hand side and kinetic energy as a vehicle, or bicycles speeds up as you
come down the hills. So all of these, these are energy
conversion processes. Some of them are more complicated than
others. Some of them are more difficult to
execute than others. But they're very important to use the
energy forms that we find available to us on Earth.
To. produce the forms of energy that we want
in order to make life more comfortable. taking an example, and I mentioned the
bicycle coasting down a hill, That converts the potential energy to kinetic
energy and I just put some numbers on here to show, you don't need to know how
to make the calculations. Some of you probably do but just as an
example, if you have a 10 ft high hill and you coast, coast down a hill this 10
ft high and you have no wind drag or wheel friction, varying friction and
rolling friction of the tire on the surface.
Then you could, the vehicle, the bicycle would accelerate 17 miles per hour.
And that would be true for a car as well as for a bicycle.
It would be, it's irrelevant of the mass. in the metric system, if it's a 3 meter
high hill And you coast down it, you'll can ideally create 28 kilometer per hour
speed. but that's the ideal, that's the upper
limit. If somebody comes to me and says he can
do better than that, then I am very skeptical about something because, it,
it's, it someway energy is being created from something else.
Are created from nothing, so this is the upper limit if we have a friction-less
process, ideal friction-less process with no wind drag and no rolling friction.
but total energy is not created. Energy is merely converted from potential
energy to kinetic in this, so this a, a good practical example, one that you
could probably intuitively understand. But of course, we do the opposite when
we, when we climb back up the hill. We're adding potential energy to
ourselves and to the bicycle so that we can coast down.
On the other side. Another example is we take natural gas
chemical energy and we burn it with the oxygen in the air.
Furnace is shown on the right hand side, that's a typical warm air furnace as we
call it in the US. The European Western European and in
other countries. Don't have as many of the warm air
furnaces, they have more water radiators. But this one burns natural gas and
releases a chemical energy into a flame and that warm thermal energy is then
transferred to the air that's circulated from the house and fed, then blown with a
fan back into the house. So warm air heat is added back to the air
in the house. from the chemical start what, the energy
that started off as chemical energy in the natural gas.
So, the gas furnace is a nice energy conversion device.
Converting chemical energy to chemical energy or heat.
[SOUND] so those are some examples and trying to get a little better handle on
what we mean when we talk about energy is conserved.
Total energy conserved not kinetic energy is conserved or potential energy is
conserved or chemical energy is conserved.
But total energy of all of the those added together of the Earth are in our
box that we're dealing with. you can't, can have more energy coming
out than you have going in. Okay, thank you.
Next time we'll deal with the second law in a little bit more detail.
Thank you.