Thermal Equilibrium Video Lecture | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Hi. It’s Mr. Andersen and this is AP Physics
essentials video 132 on thermal equilibrium,
which is a complex way of saying if we have
two objects that are connected, they have
different temperatures, eventually they will
end up at the same temperature. And two things
in my computer right now that are generating
heat are the graphics processor and the CPU.
And so as they do calculations they generate
heat and that could damage the computer. And
so what scientists use is a cooler object,
called a heat sync. And what happens is as
it is connected to those other processors
it is transferring heat to the heat sync and
then lots of times a fan will blow that away.
And so if you have two objects with varying
temperatures, what will happen? Thermal energy
will be transferred from the higher temperature
to the lower temperature. And eventually they
will achieve thermal equilibrium. What does
that mean? They are the same exact temperature.
And so the amount of thermal energy that is
transferred from the hotter to the colder
object is related to the mass of the object
and also the temperature. So if the object
on the left is much more massive then the
one on the right, and a higher temperature,
it is going to transfer more energy then if
it had a lower mass and a lower temperature.
And this is all based on conservation of momentum.
So the molecules on the left side, when it
was warmer are moving faster. As the collide
with those on the right side they are transferring
that momentum to the right side. And so eventually,
since momentum is conserved, they all eventually
have the same temperature over time as those
collisions start to equalize. So if we look
at a simulation of that, I am going to take
an iron object and I am going to put it on
a brick object and we can see that the temperatures
do not change. And the reason why is they
have the same temperature. Now let me heat
up the iron, so I am giving it a higher amount
of kinetic energy. The molecules are moving
around. We can measure that by using a thermometer.
Now what happens as I put it on the brick?
You can see that it is lowering the temperature.
But where is that energy going? It is going
to the brick itself. What happens after time?
Eventually, we have done it right now, we
have achieved thermal equilibrium. They are
going to be the same temperature. I could
do the same thing with the water. So I am
going to heat up the iron. I am adding more
energy to those molecules. They have a higher
amount of momentum. What happens when I throw
it into the water? You can see there is a
decrease in the temperature of the iron. Increase
in temperature of the water. Eventually due
to conservation of momentum they are the same.
What happens if I cool it down, so now I am
removing energy from that. It is actually
going into the ice itself? What happens? Now
I see a decrease in the water, increase in
the iron. And so it is easy to figure out
where that thermal energy is going. It is
always going from the higher object or the
hotter object to the colder object. Now this
is macroscopically looking at it. What happens
microscopically? Well if you look at it, let’s
say we have these two objects, the one on
the left and the one on the right. Which one
has a higher temperature? Well it is going
to be the one on the left. You can see the
molecules are going faster. They have higher
kinetic energy. But watch what happens. And
it will be really subtle, but I am going to
connect these two together. The one on the
left remember is going to have higher molecule
speed then the ones on the right. And so if
we watch what happens when they are connected,
you can see they are colliding along that
margin. And as they are colliding along the
margin they are transferring some of that
momentum. What happens eventually, they end
up at the same molecular motion or the same
temperature. And did you learn to construct
an explanation for what is going on as we
achieve thermal equilibrium? Not only at the
macroscopic level but the microscopic? I hope so.
And I hope that was helpful.