Examples of First Law of Thermodynamics / Law of conservation of Energy

You have definitely seen this in Diwali or in Christmas celebrations.

What happens here?

The chemical energy of the cracker (rocket) is converted to heat and sound energy in the sky.

Well, this is an example of first law of thermodynamics.

I’ll explain you many more examples based on the first law of thermodynamics that you have already experienced in everyday life.

I’ll also give you the real life examples based on the equation (∆E = Q – W), which is a mathematical form of first law of thermodynamics.

Before moving to the examples, if you do not know what the first law of thermodynamics is, then kindly visit this “Detailed article on first law of thermodynamics.”

Just read this short and sweet statement of 1st law of thermodynamics.

“Energy can neither be created nor can be destroyed but transformation of one form into another form can be possible.”

Now, let’s get started with the examples of first law of thermodynamics / law of conservation of energy.

Daily life examples of First law of Thermodynamics

1) Conversion of electrical energy into mechanical energy.

The electrical energy is converted into mechanical energy of a fan.

You might have seen this. Right?

Home appliances like table fan, ceiling fan, electric motor, grinder, mixer, washing machine, etc use electrical energy and convert it into a rotational motion.

This is how one energy is converted into the other energy.

2) Conversion of heat energy into mechanical energy

Heat engines work on this principle.

The heat energy of the fuel is converted into a mechanical energy as shown in the above image.

When the fuel is ignited inside the cylinder, it produces heat energy. Because of this heat energy, the higher temperature is created inside the cylinder. Because of this, the expansion of the piston takes place which in turn produces the rotational effect as shown in above animation of heat energy.

Thus, this is the example of first law of thermodynamics or you can say example of law of conservation of energy in which heat energy of fuel is converted into mechanical energy.

3) Conversion of heat energy into chemical energy

You have studied about photosynthesis in your previous standards. 

Do you know how a plant grows?

They use solar energy for their growth.

Plants absorb solar energy through solar radiations and they convert this solar energy into chemical energy.

This is nothing but a conversion of one energy into another (heat energy into chemical energy)

In this way, law of conservation of energy appears in this example.

4) Conversion of electrical energy into heat energy

Now, what happens here?

How does an electric heater work?

There is a heating coil as shown in the image which uses electrical energy and converts this electrical energy into heat energy. 

Thus, this is a simple daily life example of first law of thermodynamics which shows the conversion of electrical energy into heat energy.

These type of electrical heaters are used in bathroom water heaters as well as water heater for a fish tank.

5) Conversion of chemical energy into heat and sound energy

Well, I give you little bit idea about this example in very beginning of this article. 

Now look, as you can see in the animation, the rocket contains some chemicals. So we can say that it possesses chemical energy. 

When we ignite this rocket, the rocket goes up in the sky and boom…

This chemical energy stored in the rocket is converted into a heat energy as well as sound energy.

Thus, here also the energy remains conserved. This is why the first law of thermodynamics is also known as the law of conservation of energy.

Now I want to explain to you how potential energy is converted into kinetic energy.

But let me tell you what is potential energy and what is kinetic energy.

Potential energy: Potential energy is the energy stored in a body due to its position with respect to some other body.

Kinetic energy: Kinetic energy is the energy which an object possesses due to its motion.

6) Conversion of potential energy into kinetic energy

This picture shows that a boy is holding the stone in his hand.

Now just think, what type of energy does this stone possess?

It’s potential energy. Right?

Because you can see that the stone is at some height.

Now, what will happen when this boy will release the stone?

The stone will come in motion and it comes down.

Now you think, which energy will this stone possess?

It’s a kinetic energy. Right?

Thus, the potential energy of the stone is converted into a kinetic energy. 

Here also the energy is conserved.

Hence, this real life example of first law of thermodynamics shows the conversion of potential energy into kinetic energy.

7) Conversion of sound energy into electrical energy

In a microphone, the sound waves are absorbed and it is converted into electrical signals. These electrical signals are further transferred to the amplifier and other components of the sound system.

Isn’t it an amazing real life example of law of conservation of energy / 1st law of thermodynamics.

8) Conversion of electrical energy into sound energy

What happens in speakers or other Sound systems?

The speakers work on electricity. Speakers or other Sound systems use electrical energy and produce sounds. This shows a conversion of electrical energy into sound energy.

9) Conversion of mechanical energy into electrical energy

Do you know what is the function of generator?

Generator uses fuel to produce mechanical energy and then this mechanical energy is used to produce electricity.

Hence this is an example in which chemical energy of fuel is converted into mechanical energy and then this mechanical energy is converted into electrical energy.

So many energies in a single picture (short and sweet)

Well, I’ll show you so many energies converting from one form to another in a single picture.

Just observe these everyday life examples of first law of thermodynamics mentioned in the below image and you will definitely understand it.

I hope you have understood this above example of law of conservation of energy.

(Explanation of above image: 

As you can see, the sun contains UV radiation which is absorbed by the plants and trees. Plants absorb this solar radiation and store it in the form of chemical energy.

Again, these plants are eaten by the animals (herbivores animals) so the energy is again stored in the animals body as a chemical energy.

Also when the plants and animals die, they get buried in the earth which produces fossil fuels after many years due to decomposition. This fossil fuel also contains chemical energy.

This chemical energy is used in electric batteries to produce electrical energy.

Also this fuel containing chemical energy is used in power plants to produce electricity.

You can see in the image that the rocket or space shuttle uses chemicals of the fuel for its motion. Thus the chemical energy is also converted into mechanical energy.

Now, you all know about electric cars. Electric cars use electric batteries. Thus the electric energy of the battery is converted into motion of a car (kinetic energy).

Now you watch the television daily and you also have a bulb in your room. What type of energy conversions take place here?

In television, the electrical energy is converted into light energy and sound energy. While in a bulb, the electrical energy is converted into light energy. 

I hope you have clearly understood the example of first law of thermodynamics / law of conservation of energy with all the cluster of energy conversions in a single picture.)

Simple example based on the mathematical equation (∆E = Q – W)

Before moving to the example, first of all let us recall the statement of first law of thermodynamics in terms of heat, internal energy and work.

“First law of thermodynamics: The net change in total energy of a system (∆E) is equal to the heat added to the system (Q) minus work done by the system (W).”

Now, I’ll explain the example of first law of thermodynamics based on this statement.

This boy takes the energy drink and he gains Q amount of energy from it. We can say that Q amount of energy is entering the body.

Now what have you noticed from the above Image? You can see that this muscular boy has gained Q amount of energy and now he is ready to do work. Right now, he is having total energy E1. 

Now this muscular boy spends some W amount of energy in doing work (here weight lifting). After doing this work, his total energy becomes E2.

Now, let us relate the entire example with the equation.

It’s easy. Don’t worry. 

Now here,

Q = Inlet energy to the body

W = Outlet energy in the form of work

E1 = Total energy that boy is having during initial state

E2 = Total energy that boy is having during the final state

Here, the body gains Q amount of energy as shown in the above image. And after sometime the body is spending some W amount of energy in doing work.

Hence the net change in total energy of the body is given by Q – W.

I told you guys that the boys total energy was E1 and then it became E2. Thus, this change in total energy is nothing but E2 – E1.

Above statement can be mathematically written as;

E2 – E1 = Q – W

Therefore, ∆E = Q – W

I hope you have clearly understood the everyday life examples of first law of thermodynamics using its mathematical form.

Important Guides for you

Also read:

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• What is the definition of entropy in thermodynamics?
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• What is Thermodynamic Equilibrium? (With Best Example)
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• What is Thermodynamic System? – Open, Closed & Isolated system (With Examples)