Types of Energy and Forms of Energy

Types of energy (kinetic energy and potential energy) for doing work can exist in several basic forms such as chemical, electrical, radiant, mechanical, thermal, and nuclear energy. Other forms of energy that are learned in chemistry and physics are sound, electromagnetic radiation, surface, ionization energy, etc. These various forms obtained from kinetic or potential types of energy have been obtained from various natural phenomena and according to the law of conservation of energy, each of these forms is converted to another form.

The Law of conservation of energy states that energy can neither be created nor destroyed but may be transferred from one form to another. For example, when we burn wood or fuel like gasoline or natural gas, it changes chemical energy to thermal or mechanical energy.

Heat Energy

Heat is a form of thermal energy that can yield work or can be produced from work. If heat is obtained from work, the amount of heat produced is proportional to the work spent by the system. When heat is transferred into work, there is proportionality between the work spent and heat disappearing.

All states of matter contain heat energy and is transferred from one object to another. The transfer or flow of energy due to the difference in temperature between the two objects is called heat. It causes the movement of atoms, molecules, or ions in solids, liquids, and gases.

Unit of Heat Energy

Heat is a form of thermal energy, measured by SI unit joule (J) in honour of the English English physicist and mathematician James Prescott Joule. British thermal unit (BTU) and calorie (cal) are also used in many branches of science and engineering.

• Calorie: One calorie is the amount of heat required to raise the temperature of 1 gram of water from 14.5 degrees Celsius to 15.5 degrees Celsius at one atmospheric standard pressure.
• British thermal unit (Btu or BTU): One BTU is the amount of heat required to raise the temperature of 1 pound of liquid water by 1 degree Fahrenheit at one atmospheric standard pressure.

Kinetic Energy

Kinetic energy is a type of energy that is obtained by the motion of an object. For example, walking, falling, flying, and throwing. After gaining this type of energy, the object maintains a fixed kinetic energy unless its speed changes.

Calculation of Kinetic Energy

The kinetic energy of a moving object is calculated by the amount of work that can be done before coming to rest.

Consider an object of mass m moving with a uniform velocity u. The force F is applied to the object and displaces the object through a distance s and it attains a velocity v.

The work done by the object,
W = Fs

According to the equation of motion,
v² − u² = 2as
where a = uniform acceleration
u = initial velocity
v = final velocity
∴ s = (v² − u²)/2a

From Newton’s Law of Motion, F = ma
Therefore, W = mas
Substituting the value of s, we have
W = m(v² − u²)/2

If initial velocity, u = 0
Then, W = mv²/2

Such work is equal to the kinetic energy of the object.
∴ KE = mv²/2

Problem: A bullet of mass 8 g fired with a velocity of 100 ms⁻¹. How to calculate the kinetic energy of such a type of bullet?

Solution: From the above problem,
Mass (m) = 8 g = 8/1000 = 0.008 kg
velocity = 100 ms⁻¹

Therefore, the KE of the bullet = mv²/2
= (0.008 × 100²)/2
= 40 kgms⁻¹ = 40 J

Potential Energy

In the study of chemistry and physics, potential energy (PE) is the energy held by a body due to its change in position or shape. Gravitational, elastic, chemical, and electric potential energies are the common types of potential energy that can be measured by unit (SI) joule.

It is stored energy that can be measured by the amount of work done by the object. The most common examples of potential energy are:

• Water in a lake or dam has PE due to its position at a height.
• A book lying on a table has PE due to its position at a height.
• A wound spring of a watch has PE due to its shape.

Gravitational Potential Energy

The energy of an object increses when the object rises through a certain height above the ground. The energy present in such an object is the gravitational potential energy.

Consider an object of mass m, lying at point A on the Earth’s surface. Here, its potential energy is zero and its weight mg acts vertically downwards. To lift the object to another position B at a high h, we have to apply a minimum force that is equal to mg in the upward direction.

Work is done on the body against the force of gravity.
Therefore, Work done = Force × Displacement
∴ W = F × s

Here F = mg and s = h
Therefore, W = mg × h = mgh

The work done is equal to the body’s gain in energy (PE).
Therefore, PE = mgh

It is the gravitational potential energy of the body. The work done by gravity depends on the difference in vertical heights of the initial and final positions of the object. It does not on the path along which the object is moved.

Different Forms of Energy

Kinetic energy and potential energy for doing work can exist in the following basic forms:

• Chemical Energy
• Electrical Energy
• Mechanical Energy
• Electromagnetic Energy
• Thermal Energy
• Nuclear Energy

Chemical Energy

Chemical energy is a form of potential energy stored within a chemical substance or molecule due to chemical bonding between atoms. It can be absorbed or released during chemical reactions or heating.

Chemical Energy in Everyday Life

Batteries, food, fuels, and sugar are the most commonly used media in everyday life for storing or conserving chemical energy.

• Electrical energy can be converted to chemical energy or vice versa through an electrochemical cell or batteries through electrolysis.
• When fuels are burned, the chemical energy in fuels is converted to heat and light energy. The carbon and hydrogen or hydrocarbon present in the fuel also reacts with oxygen present in the air to form carbon dioxide and water vapour.
• Plants use sunlight, water, and carbon dioxide to produce oxygen and chemical energy in the form of sugar through the process of photosynthesis. The solar energy from the sun is used for combining hydrogen, carbon, and oxygen atoms to form sugar.
• Most of the energy used by humans derives from aerobic respiration or a combination of carbohydrates, fats, and proteins with oxygen from the air. Other types of nutrients such as water, minerals, vitamins, cholesterol, and fiber may provide little or no chemical energy but they are necessary to maintain our good health.

Electrical Energy

Electrical energy is the form of potential energy resulting from the flow of charged particles most commonly electrons particles in wire. It is the most common form which can be easily converted into other forms of energy.

Electricity generation is a process that produces electrical energy from other types of energy. The fundamental principle for the generation of electricity was discovered during the 18th century by the British scientist Michael Faraday. The Faraday electricity generation principle is still used today for generating electricity.

In a power station, electricity is generated by electromechanical generators driven most commonly by fossil fuels, nuclear fission of nuclear fuels, and flowing water and wind.

Mechanical Energy

Mechanical energy is the sum of potential energy (PE) and kinetic energy (KE) obtained by the motion and change of position of an object.

It can be measured by the formula,
mechanical energy = KE + PE
= mv²/2 + mgh

Conversion of Mechanical Energy

Today we use various types of technology and devices that convert mechanical energy into other forms of energy or other forms of energy to mechanical energy. Examples of such types of technology and devices for the production of various forms of energy are:

• Electric motors convert electricity into mechanical energy.
• Turbogenerators convert mechanical energy into electricity.
• In hydropower, the mechanical energy of storage water is converted into electricity.
• A turbine converts the kinetic energy of gas or liquid into electrical energy.
• A stream engine converts thermal energy into mechanical energy.

Radiant Energy

Radiant energy is the form of energy produced from the movement of electromagnetic waves or light. It is most commonly used in the fields of radiometry, solar radiation, heating, and lighting.

Radiant energy travels in waves and types of waves with higher frequency are higher energy. When the power of the radiant source is increased, the LED light emits more light because more photons are radiating off in all directions.

Forms of Radiant Energy

The main forms of radiant energy may include the entire radiation of the electromagnetic spectrum such as gamma rays, x-rays, radio frequencies, and microwaves.

• Visible light such as sunlight carries radiant energy which is stored as chemical energy through the process of photosynthesis.
• Nuclear power plants use this type of energy for boiling water which drives steam turbines for the production of electricity.
• Sun is a naturally occurring radiant source that can convert radiant energy into usable electricity or use it for heating water.

Form of Thermal Energy

Thermal energy is a type of heat energy or energy carried by a system or object due to the movement or vibration of its molecules. It is a kinetic type of energy due to the movement of particles. Heat or thermal energy obtained from different sources is directly related to temperature.

Hot tea is cool in the room due to the loss of some thermal energy. Therefore, heat flows from the tea to the room by slowing the vibration of tea molecules over time. The tea cools to the same temperature carried by the room.

Nuclear Energy

Nuclear energy is the form of energy released due to the splitting of atomic nuclei. It can be generated or obtained from nuclear fission, nuclear decay, and nuclear fusion reactions.

We used nuclear fission reactions for the production of usable nuclear power. Nuclear power plants generate electricity by using thermal energy released from nuclear fission reactors. Today, a wide range of electricity generated from nuclear power plants is produced by nuclear fission of uranium and plutonium.

The nuclear fusion reaction that occurs in the interior of the Sun is the main source of our global energy. A nuclear chain reaction takes place in the interior of the Sun. The sun is made up of about 75 percent hydrogen (H) and 25 percent helium (He).

During nuclear fusion, the immense pressure and temperature in the interior of the Sun make nuclei distinct from their electrons. A huge amount of heat and light energy is emitted from the Sun when hydrogen nuclei combine and generate one helium atom.

Different Types of Energy Sources

Different forms of energy sources that we use in our daily lives can be classified into two types:

1. Nonrenewable sources
2. Renewable sources

Nonrenewable Types of Energy Sources

A non-renewable source is a finite natural resource of energy that cannot be readily replaced after its consumption. The by-products of non-renewable energy resources may cause environmental pollution. Most of the energy used by human society comes from nonrenewable fossil fuels because such types of sources are affordable to use and transport.

Fossil fuels (oil, natural gas, and coal) are the main types of nonrenewable resources that are used widely to fulfill our daily energy needs. We use it every day for fueling our cars and heating our homes. Most of the electricity used in our homes is generated through fossil fuels.

What are Fossil Fuels?

The three types of energy sources such as oil, natural gas, and coal are collectively called fossil fuels. These fuels are formed from dead plants and animals over millions of years.

All types of energy obtained from fossil fuels originally come from the Sun. Solar energy is stored in plant tissue in the form of chemical energy through the process of photosynthesis. When animals consume foods from plant sources, they add such chemical energy to their own bodies. After burning fossil fuels, such trapped energy is released and used according to our daily requirements.

These fossil fuels are found in underground layers of rock and sediment. Pressure and heat worked together for the transformation of dead plants and animals into crude petroleum oil, coal, and natural gas.

The burning of fossil fuels releases carbon dioxide into the earth’s atmosphere. Rising levels of heat-trapping carbon dioxide in the atmosphere cause greenhouse effects and increase the temperature of the earth or global warming.

What are Nuclear Fuels?

Nuclear fuels are materials used in nuclear power stations for the production of electricity from the heat by turbines. Heat is generated when fuels in nuclear power plants undergo nuclear fission.

Today, uranium and plutonium are the most common fission fuel used for the production of nuclear power. Nuclear power obtained from nuclear fuels provides a significant part of electricity in various countries of the world.

Renewable Energy Sources

Renewable types of energy are clean sources of energy that are obtained from infinite natural resources and replaced after their consumption.

The most popular energy obtained from various types of natural phenomena such as sunlight, wind, water flow, tides, plant growth, and geothermal heat may include:

• Solar energy
• Wind energy
• Hydropower
• Tidal energy
• Geothermal energy
• Biomass energy

Natural resources such as wind, water, solar, biofuel, and geothermal energy are types of renewable energy sources because these sources can be renewed by natural processes or they can be continuously available in nature.

Solar Energy

Solar energy is a form of renewable energy that converts sunlight into solar power through solar technologies. Such types of technologies are used for the conversion of energy obtained from sunlight into electricity.

A large magnitude of solar energy is used as a source of electricity in different parts of the world. Active solar technologies may use photovoltaic (PV) systems, concentrated solar power, and solar water heating systems to acquire such types of energy.

• Solar cells: Photovoltaic cells convert sunlight into an electric current for small and medium-sized gadgets.
• Solar system: Commercial concentrated solar systems use sunlight of a large region by lenses or mirrors to produce electricity.
• Solar cooker: In a solar cooker sunlight is converted to heat energy that we use for cooking.

Solar energy is an example of a sustainable type of energy resource. It helps us lower electricity bills and carbon footprints in our environment but has several disadvantages.

• Such types of energy sources are available only during the daytime.
• The production of solar energy is very low or not available in cloudy weather.

Wind Energy

Wind power is a form of energy that uses the kinetic energy of air to generate electricity by wind turbines. Historically, wind power is used for milling and pumping.

The power obtained from wind depends mainly on airspeed and geological location. Therefore, the areas where wind flow is stronger and more constant are preferred locations for wind farms.

Wind-generated electricity contributes a significant amount of electricity required in the United States and other well-developed countries. But it has several disadvantages which include:

• A large number of wind generator covers a large area for the production of comparatively low amounts of electric power.
• When the wind does not blow, wind generators remain dead.

Hydropower

Hydropower or hydroelectric power is one of the common and oldest renewable types of energy sources that use the natural flow of moving water to generate electricity by turbines. It not only converts the kinetic energy of water to electricity but also helps in flood control, irrigation support, and clean drinking water.

Hydropower is an attractive alternative resource to fossil fuels because it does not emit any carbon dioxide or other toxic pollutants and it provides a relatively consistent source of energy. Therefore, a significant part of global electrical energy demand has been fulfilled by hydroelectric power plants situated in various parts of the world.

Tidal Energy

After the development of modern technology, a type of power produced by the natural rise and fall of tides due to gravitational interaction between the earth, sun, and moon. The tides of ocean water are used to transform mechanical energy into electricity in various ways.

Tidal energy is uniform and reliable because it is based on the rise and fall of tides. But other forms of renewable energy sources such as wind and solar energy are dependent on random weather patterns.

Biomass Energy

The word biomass refers to organic substances that store energy during the process of photosynthesis. Generally, biogas refers to a mixture of different gases produced by various biochemical decomposition of organic matter. These organic matter are agricultural waste, manure, municipal waste, plant material, sewage, food waste, etc.

Biogas is an excellent fuel for burning because it contains a high percentage of methane gas. It does not give too much smoke during the burning. Compressed natural gas (CNG) is a biogas that has been obtained after the technological development of biogas. It is a good fuel for our vehicles.

Geothermal Energy

Geothermal energy is thermal or heat energy stored in the earth’s interior. It can be generated by utilizing the heat of the earth’s interior. Geothermal energy can be used for space heating, or boiling water and generate streams to drive turbogenerators.

Fluids drawn during geothermal power generation carry a mixture of gasses such as carbon dioxide (CO₂), hydrogen sulfide (H₂S), methane (CH₄), and ammonia (NH₃). All of these pollutants contribute to global warming and acid rain but the contribution is very small compared to fossil fuels.

Unlike wind and solar types of energy, geothermal power plants produce power at a constant rate because it does not depend on weather conditions.

Frequently Asked Questions – FAQs

What are the two main types of energy?

Kinetic and potential energy are the two main types of energy obtained from various natural phenomena. All other forms of energy (chemical, electrical, radiant, mechanical, thermal, nuclear energy, etc) are obtained from kinetic and potential types of energy.

What is the human energy?

Most of the energy used by humans derives from aerobic respiration or a combination of carbohydrates, fats, and proteins with oxygen from the air. Therefore, human energy is the chemical energy stored in the human body or foods they eat.

Other types of nutrients such as water, minerals, vitamins, cholesterol, and fiber may also provide little or no chemical energy but they are necessary to maintain our good health.

What is the main source of energy?

The sun is the main source of various types of energy that we find on our earth. All the renewable and nonrenewable types of energy come mainly from our Sun.

• The nonrenewable energy from fossil fuels is stored as chemical energy during photosynthesis.
• Similarly, in the production of renewable types of energy, our sun is directly or indirectly involved in such power generation.

What energy sources are renewable?

Wind flow, water flow, solar radiation, biomass, tides, and thermal or heat energy stored in the earth’s interior are the main natural renewable types of energy sources found in our earth. These types of energy sources are renewable because these resources can renewed by various natural processes or continuously available in nature.