According to the Law of Conservation of Energy, we can’t create or destroy energy here on the planet, energy can only be transformed or transferred from one form of energy to another.
Energy represents the ability to do work and is important to be informed about all the energy forms available today because this way we can better understand the world we live in.
Forms of Energy
The different forms of energy known today include kinetic energy, potential energy, thermal energy, electrical energy, chemical energy, gravitational energy, radiant energy, mechanical energy, sound energy, elastic potential energy, light energy (solar energy), rotational energy, magnetic energy, electric potential energy, surface energy and binding energy.
1. Kinetic Energy
Kinetic energy is the energy of motion, and represents the energy of an object that has mass and velocity.
Any object that has mass and moves from one direction to another or rotates has kinetic energy.
The rotating object has rotational kinetic energy because instead of using its velocity it uses its angular velocity.
Kinetic energy equation
KE = 1/2mv2
By knowing the mass (m) and the velocity (v) of a moving object, we can measure the value of its kinetic energy in Joules (J).
A rotating object that has mass has rotational kinetic energy.
KE = 1/2IĻ2
In this equation, we have the rotational inertia (I), and the angular velocity (Ļ) of the object.
2. Potential Energy
Potential energy is energy due to position, but must be positioned where we can get the energy back out again.
On Earth, by lifting an object we can say that the object has potential energy due to the presence of a conservative force which is the gravity.
However, if we don’t lift the object, but we move it on a surface, there will be no potential energy stored in the object because there are no conservative forces involved here.
Potential energy equation
If gravity is involved, we have gravitational potential energy (PEgrav).
PEgrav = mgh
In this equation we have gravitational potential energy (PEgrav), the mass of the object (m), the gravitation force, which is a conservative force (9.8 N/kg on planet Earth), and the height of the object (h).
In the case of a mass-spring oscillator, we have a ball attached to the spring, and if we push the ball back to compress the spring, we gonna have potential energy stored in the ball.
The equation looks a little different here.
Us = 1/2kx2
Where (Us) is the potential energy of the spring, (k) is the spring constant, and (x) is the displacement or how far move the ball.
There are also conservative forces when we work with charges.
If we do work on a charge to move it in an electric field we gonna get that energy back.
In the case of an electric circuit (a battery connected to a light bulb), the positive charge will move from the negative end of the battery through the circuit and towards the light bulb due to the fact that we do work on it, and from the light bulb, the charge will return to the positive end of the battery and will close the circuit.
We have here potential electric energy that can be calculated using the following formula:
ĪUE = qĪV
ĪUE is the amount of potential electric energy that is equal with the charge (q), times the change in voltage (ĪV).
3. Thermal Energy
Thermal energy represents the total energy of all the particles in an object, and depends on the temperature of the object and the number of particles in that object.
The more particles an object has at a specific temperature, the more thermal energy it has.
What is heat?
Heat is the transfer of thermal energy from a warmer object to a cooler object.
Due to the heat transfer, the warmer object will cool down and the cooler object will warm up until will reach the same temperature as the warmer object.
Solar thermal power plant in Australia, source: pixabay.com
The heat transfer will stop when both objects will have the same temperature.
Heat is measured in Joules (J).
Heat can be transferred in three different ways.
1. Convection:
transfers heat through fluids such as liquids and gases (water, air, etc.).
When air is heated it becomes less dense, and it starts to move up.
Cooler air becomes more dense and starts moving down.
The heat source for the air in our atmosphere is the Sun, and the up and down movement of the warmer/cooler air in the atmosphere causes a convection current that generates the wind and different weather patterns.
2. Conduction:
transfers heat between two objects (from one particle to another).
Let’s say that we heat up milk.
The particles from the pot will touch the particles of the milk, and because the pot is hot, the particles will move faster.
When the fast moving particles of the pot are touching the milk particles, these will also start moving faster, generating heat and making the milk hot.
3. Radiation:
is the transfer of energy using electromagnetic waves.
Radiation works without the presence of matter, and this is the reason why we can feel the radiation of an object without touching it (we feel the heat of the Sun without touching it).
A material that conducts heat well is called a conductor (metals are a good example here).
A material that conducts heat poorly (opposite to the conductor) is called an insulator (wool, plastic, glass, etc.).
4. Electrical Energy
Electrical energy is the energy stored in charged particles within an electric field.
Charged particles are creating the electric field that exerts a force on other charged particles within the field.
The electric field applies the force on the charged particles causing them to move (to do work) and this is what we call electrical energy.
5. Chemical Energy
Chemical energy is the energy stored in a substance or in materials.
Examples of Chemical Energy
A candle consists of a solid substance such as wax or tallow (these being both flammable substances).
When we ignite the candle, a chemical change happens and the chemical energy stored in the wax or tallow is transformed into thermal and light energy.
The flame of the candle produces light and radiates heat.
The food that we eat daily contain chemical energy.
The energy is released when food is digested in the presence of oxygen in our body.
In fact, chemical energy is released when a chemical reaction takes place.
6. Gravitational Energy
Gravitational energy represents the potential energy of a body that has mass and is in relation with a massive object due to the presence of gravity.
It refers to the potential energy in relation to the gravitational field, and can be calculated if we know the masses of the two bodies, the distance between them and the gravitational constant (G).
As example we can a take a ball that falls to the ground from a certain height.
In this case, the gravitational potential energy (U) has the following formula:
U = mgh
In this equation, (U) is the gravitational potential energy, (m) is the mass of the ball, (g) is the gravitational acceleration and (h) is the distance between the two bodies (the height from which the ball falls to the ground).
7. Radiant Energy
Radiation or radiant energy represents the energy transmitted through electromagnetic or gravitational waves.
Radiant energy is measured in Joules (J).
Examples of Rdiant Energy
The sunlight carries radiant energy, which is used by solar panels or mirrors to produce electrical energy or heat energy.
A burning candle produces radiant energy, light energy and also heat energy. Heat is actually radiated in the surrounding space around the candle due to the presence of the flame.
8. Mechanical Energy
Mechanical energy refers to the kinetic energy of an object due to its motion.
We can also say that mechanical energy is potential energy of an object due to its position.
Examples of Mechanical Energy
An electric motor converts electrical energy into mechanical energy.
A wind turbine rotates due to the action of the kinetic energy of the wind, and the rotation of the propeller that is transferred to the generator is actually mechanical energy.
The generator will turn mechanical energy into electrical energy.
9. Sound Energy
Sound is also a form of energy, and is produced by vibrations.
We can hear the surrounding sounds due to the fact that the sound waves present in our space are striking the eardrum, which begins to vibrate.
The vibration of the eardrum makes us to hear a significant part of the surrounding sounds.
In air, sound waves propagate with the speed of 340 meters/second, so in the case of a storm with thunders, the very loud sound produced by a thunder will make our windows and doors to vibrate due to the fact that the thunder produces sound energy.
By knowing the speed of the sound energy (the speed of the sound waves in different environments) we can measure the distance between the thunder (the storm) and us by measuring the time (in seconds) from the moment when we see the lightning and the moment when we hear the thunder.
10. Elastic Potential Energy
Elastic potential energy is the energy that is stored in elastic materials or objects (a rubber band, a spring, etc.).
By compressing the spring, the force that is applied to the spring is stored in the spring as elastic potential energy.
Once we move our hands, the stored energy in the spring will be released right away and will make the spring bounce back and return to its original position.
We have a similar phenomenon when we stretch the spring.
The force applied by us to stretch the spring will store elastic potential energy in the spring.
Once we move our hands, the stored elastic potential energy will be released very quickly and will help the spring to return to its original position.
11. Light Energy
Light is produced today by natural (the Sun) and man-made sources (a light bulb, candle, etc.), and is the source of life for all the living beings on the planet.
Our natural source of light is the Sun, which is a star that produces light and heat energy (among others) due to the nuclear fusion reaction that takes place every second in its core.
Mankind uses today the sunlight (solar energy) to generate clean electricity (electrical energy) and heat energy (with the help of mirrors).
12. Rotational Energy
Rotational energy is a form of kinetic energy (angular kinetic energy) due to the fact that the object rotates, and the rotational energy is part of its total kinetic energy.
In the case of an object that rotates around a single axis (a one-dimensional rotation), the rotational energy of the object has the following formula.
Erotational = 1/2IĻ2
where (E) is the kinetic rotational energy, (I) is the moment of inertia (around the axis of rotation), and (Ļ) is the angular velocity of the object.
13. Magnetic Energy
Magnets have energy and they can be used as toys and also to power large things such as a roller coaster or high-speed Maglev trains.
A magnet has potential magnetic energy, which can used to create large amounts of kinetic energy.
The magnetic field is the area surrounding the magnet.
Any magnet has two poles, one being the north pole and the other the south pole.
Similar magnetic poles repel each other, but if we put together different magnetic ends they will attract each other.
The magnetic potential energy of a magnet depends on the location of the poles, the strength of the magnetic field, and the distance apart.
The magnetic potential energy of the magnet increases when we put together similar magnetic poles (the closer they are the stronger is the magnetic potential energy).
If we put together different magnetic poles they will attract each other and the magnetic potential energy will be drastically reduced.
Magnetic potential energy increases as the opposing poles move away from each other.
14. Electric Potential Energy
Let’s say that we have a system composed of two positive charges.
If we put together these two charges they will repel each other and will start moving away one from the other.
When they move away, they start gaining kinetic energy.
Well, the source of this kinetic energy (of the two charges) is the electrical potential energy.
At the beginning, in the system we had the two positive charges and there was electrical potential energy.
When the two positive charges have started to repel each other, the electrical potential energy has been turned into kinetic energy.
The less electrical potential energy in the system, the more kinetic energy.
However, the total energy in the system remains the same.
15. Surface Energy
There is a difference of energy between the molecules within a liquid or solid and the molecules on the surface of the liquid or solid.
Surface energy can be defined as the excess energy of the molecules at the surface of a material compared to the molecules within the material, and refers to the work (energy) required to build an area of a particular surface.
16. Binding Energy
Binding energy refers to the mechanical work that needs to be done against the forces that are holding an object together.
The work is required to disassemble the object into its components with enough space between them so that further separation would only require negligible additional work.
At atomic level, the binding energy of the atom is generated by electromagnetic interaction, which is mediated by photons.
In this case, binding energy refers to the work that needs to be done (energy required) to disassemble an atom into free electrons and its nucleus.
Nuclear binding energy refers to the energy required to disassemble the nucleus of an atom into free unbound neutrons and protons.
Conclusion
We are using different types of energy sources in our everyday life, some of them are friendly with the environment, while others are harmful for nature and us, and this is the reason why we need to stay well-informed on how to reduce the use of polluting power and increase the capacity and use of renewable energy.
