In physics, energy can be defined as the capacity to do work. Just like there are many different ways of doing work, there are also different types of energy.
Energy is a quantitative property. As per the law of conservation, energy can neither be created nor be destroyed. It can only be converted from one form into another.
Although calorie is the most familiar unit for measuring energy, scientists prefer to measure it in joules. One joule is equivalent to work done to move an object by a distance of 1 meter against a force of 1 newton.
Energy comes in many different forms, all of which can be categorized into two groups: potential energy and kinetic energy.
Potential energy is the energy stored in a substance or object. This stored energy is based on the state or position of a substance or object.
You can imagine this as an energy that has some “potential” to do work. When the state or position of the substance/object changes, the stored energy is released and converted into another form of energy.
Kinetic energy is the energy of an object in motion. In other words, if anything is moving, it is said to have kinetic energy. The faster the object moves, the more energy it has.
Kinetic energy can be transferred between objects and converted into other forms of energy. And it must always be either a positive value or zero.
Now that you have understood the major types of energy, it is time to introduce subtypes of energy that an object or system can possess.
|Potential Energy||Kinetic Energy|
1. Gravitational Energy
A form of Potential Energy due to gravity
As the name suggests, gravitational energy is associated with gravity. It is the energy stored in an object due to its height above the Earth.
Earth’s gravity is what holds everything close to the planet and causes objects to fall. Some of you may be surprised to know that every object, including the human body, has its own gravity. The more massive the object is, the more gravity it has. Since our body’s gravity is far fainter than the Earth’s, we don’t notice it at all.
Example: In a roller coaster, gravity applies a constant downward force on cars. The coaster tracks control the way the cars fall. When tracks slope down, gravity accelerates the car by pulling it towards the ground. When tracks tilt-up, gravity deaccelerates the car by applying a downward force.
Supermassive black holes have the strongest gravitational pull in the whole universe. They exhibit gravitational acceleration so strong that nothing — not even light — can escape from it.
2. Mechanical Energy
The sum of Potential Energy and Kinetic Energy
Mechanical Energy is the energy associated with the position and motion of an object. The mechanical energy of a perfect isolated system remains constant in time.
In the real world, however, nothing is perfect: frictional forces and other non-conservative forces are always present. Thus, when energy is converted from one form to another, a significant portion is lost as heat (or as sound or in friction).
Example: A simple pendulum is a prominent example of mechanical energy. As it swings back and forth, there is a constant exchange between gravitational potential energy and kinetic energy.
The pendulum has its greatest potential energy and least kinetic energy at the extreme positions of its swing (farthest from Earth). It achieves its greatest kinetic energy and least potential energy when in the vertical position (nearest to Earth).
Since the system loses significant mechanical energy with each swing due to friction and air resistance, an external force is required to keep pendulum moving.
3. Elastic Energy
A form of Potential Energy due to the deformation of an object
Elastic energy can be stored in a flexible object when it is temporarily under stress. This energy is stored within the atomic bonds of the object when it is compressed or stretched.
Example: Elastic energy can be found in a bow and arrow, squishy balls, and coiled springs. When you compress/stretch a spring, it absorbs some energy in the form of elastic potential energy. The more your compress/stretch the string, the more work is done by you against the spring’s restoring force, and more energy is stored.
4. Chemical Energy
A type of Potential Energy due to chemical bonds
Chemical energy is the energy stored within chemical bonds of a substance. These chemical bonds link atoms with other atoms and molecules with other molecules.
Since chemical energy is stored, it’s a form of potential energy that comes from electrons’ arrangement in atoms and ions.
This type of energy is released or absorbed when a chemical reaction takes place. In most cases, heat is generated as a by-product of a chemical (exothermic) reaction.
Example: The food we eat contains a certain amount of chemical energy. Our bodies digest food by mixing it with enzymes and acids in the stomach. Carbohydrates are transformed into glucose and then released into the bloodstream. This is how we get energy, which ultimately keeps us warm, helps us grow, and move.
5. Electrical Energy
A form of Kinetic Energy that comes from the flow of electric charge
Electric energy is caused by the movements of electrons in one direction. The faster they move, the more electrical energy they carry.
Although any charged particle — such as protons, electrons, cations, anions, positrons — can produce electrical energy, the most common current carrier are electrons.
There is also static electricity that comes from a separation or imbalance of negative and positive charges on an object. This is also electrostatic potential energy. When sufficient charge builds up, electrical (kinetic) energy is discharged to form a spark (or lightning).
Example: Alternating current (AC) is a prominent example of electrical energy. It is generated by almost all power plants and used by most power distribution systems.
6. Magnetic Energy
A form of Potential Energy stored in magnets
All permanent magnets have a definable amount of energy. Magnets can be classified based on the amount of energy they store.
The energy of a magnet reduces as it works, for instance, when it attracts metal. When the metal is removed (i.e. work done in the opposite direction), the energy is refilled.
To generate a magnetic field, work must be done. The energy of a magnetic field, for example, is the energy needed to align the elementary magnets in parallel. When aligned, elementary magnets possess potential energy called magnetic field energy.
Example: SMES (short for superconducting magnetic energy storage) is an advanced technique of storing energy in a magnetic field, which is produced when DC current flows around a superconducting coil. Compared to other storage techniques, SMES provides very high power for a brief period of time.
7. Sound Energy
Movement of energy in the form of waves
Sound is the movement of energy through a medium, such as water or air. It is produced when a force causes a substance or object to vibrate.
Sound travels in the form of a mechanical wave. Unlike light, it cannot travel through a vacuum because there aren’t any atoms to transmit the vibration.
Sound a complex phenomenon with vital tuning parameters like wavelength, frequency, velocity, intensity, and amplitude. Usually, sound energy is measured by its intensity and pressure, in units called decibels and pascals.
Example: Playing a musical instrument, clapping hands, and stomping feet are all examples of sound energy.
8. Thermal Energy
A form of Kinetic Energy due to the motion of atoms and molecules
Thermal energy comes from the heated up objects. As the temperature of an object increases, its atoms and molecules move faster and collide with each other at higher rates.
The hotter the temperature of an object or system, the faster the particles move, and the higher thermal energy it has.
Example: When you place a pot of water on the stove, the internal energy of the heated element (in the stove) is transferred to the water within the pot. This ultimately raises the temperature of the water, causing water molecules to move faster.
This means a 10-ounce glass of water at 80 degrees has more thermal energy than a 10-ounce glass of water at 70 degrees.
9. Radiant Energy
A form of Kinetic Energy that travels by particles or waves
The term ‘radiant energy’ is most commonly used in the fields of lightning, heating, and solar energy. It is produced through electromagnetic waves. These waves are made up of elementary particles known as photons.
Electromagnetic waves carry energy in oscillating electric and magnetic fields. When these waves are absorbed by a substance, the energy of the waves is transformed into heat.
Long electromagnetic waves (like radio- and micro-waves) contains lower energy than shorter ones (like ultraviolet and X-rays).
Example: Light energy is a prominent example of radiant energy, which is visible to the human eye. The Sun generates a vast amount of radiant energy that is transmitted to our planet as light via a vacuum (space).
10. Nuclear energy
A form of Potential Energy stored in the nucleus (core) of the atom
Every object in the universe is made of atoms. Each atom contains electrons, protons, neutrons, and a nucleus. Unlike normal chemical reactions that form molecules, nuclear reactions involve changes in the atom’s nucleus, which ultimately causes a change in the atom itself.
When a heavy nucleus splits into lighter nuclei (fission) or nuclei combine to form a bigger and heavier nucleus (fusion), a massive amount of energy is released. This energy is called nuclear energy.
Example: Existing nuclear power plants use nuclear fission of uranium and plutonium to produce electricity. They are cheaper, more efficient, and environment-friendly than traditional plants that use coal and gas to generate electricity.
11. Ionization energy
A form of Potential Energy that binds an electron to its atom/molecule
The minimum amount of energy required to remove an electron from the isolated gaseous atom or molecule is called ionization energy. The larger the atom, the less tightly the electrons are held by the nucleus, and thus the less ionization energy it has.
Ionization energy can indicate how reaction an atom or molecule is. It can also be used to estimate the strength of chemical bonds.
Example: The ionization potential of a hydrogen atom is 13.6 electron volts (eV). This is the amount of energy you have to apply to remove an electron from the hydrogen atom.