What is Energy?

Energy in physics or chemistry is defined as a property that can be transformed into or produced from work. Kinetic and potential energy are common forms of energy. Mechanical, internal, chemical, heat, electromagnetic, and surface energy are the main types of energy obtained from various natural facts. It is measured by SI unit joule and CGS unit erg. The other most common unit of energy are calorie (cal), electronvolt (eV), and kilowatt-hour (kWh), etc. The conservation of energy states that energy can neither be created nor be destroyed but it may transfer one form to another. Therefore, the energy obtained from different types of renewable or non-renewable sources can be converted to other forms for doing useful work. In biology, living organisms get energy from food and oxygen to carry out biological processes.

different types of energy sourcesDifferent types of energy sources

Primary sources are two types such as non-renewable and renewable energy sources.

  • Oil, natural gas, coal, and nuclear power are the four major types of non-renewable natural resources which we used widely in our daily life. From these four, oil, natural gas, and coal are collectively named fossil fuels. These resources are obtained due to the decomposition of dead plants and animals over millions of years. These are mainly hydrocarbon compounds.
  • Wind, solar, geothermal, hydropower and biogas are examples of renewable sources. These types of resources we used mainly to save fossil fuel, less environmental pollution, and huge demand for energy or electricity all over the world.

These primary sources are converted to electricity, a secondary source, and transmitted to homes and factories.

What is heat energy?

Heat or specific heat is another form of energy that produces work and transferred from one body to another. But heat is different from other sources such as chemical, mechanical or electrical because all the other forms are completely converted into work but heat cannot be wholly converted into work. In learning chemistry or physics, when two objects with different temperatures come together, heat transit or flow from lower temperatures to higher temperatures.

For more precise examples of conversion of energy into work or heat are burning of coal or natural gas for doing some useful work. The mechanical work spent by rubbing two crystalline solid blocks of ice generates a quantity of heat. Therefore, there has an intimate relation between heat and work. One can yield the other quantity.

It is an extensive thermodynamics property like volume or surface area because it depends on the mass of the system. On the other hand, intensive properties like temperature, pressure, density, refractive index, etc are independent of the mass of the system.

Kinetic and potential types energy

Energy like kinetic, potential forms in physics, is the ability to transformed produced heat or doing thermal, mechanical types of work in science

What is kinetic energy?

It is the type of energy produced due to the motion of objects. It can be defined and calculated by accelerating a given mass of the body from rest to an appropriate speed. It is mainly three types rotational, vibrational, and translational energy. In classical mechanics, if the mass of the non-rotating body = m and speed of the body in a given time = v. Then the kinetic energy (KE) = mv2/2. The accelerating bodies maintain their KE unless their velocity changes.

What is potential energy?

The potential energy (PE) formula in science was described first in 19th-century Scottish engineer and physicist William Rankine to define various forms of potential energies held by an object. Gravitational, elastic, electric energy are the common types of PE. The common examples of PE are displacing the spring from its equilibrium position, lifting the weight, turning the blades in the wheel. Gravitational potential energy can be calculated by the formula, PEg = mgh, where m = mass of body whose height = h and g = gravity of earth = 9.80665 m/s2.

Unit of heat, energy, and work

Heat, energy, and work are derived from physical quantities whose unit can be derived from other base physical quantities like mass, length, and time. The units and dimensions of heat, energy, and work may be expressed in terms of base physical quantities by multiplication and division. From the definition of work, W = F × s, where the force (F) = maas × acceleration and acceleration = length sec-2. Hence, W = mass length2 sec-2.

From the definition, energy is the ability to doing work. Therefore, the unit and dimension of work and energy are the same. The most used unit of heat, energy, or work like joule, calorie, electronvolt, and kilowatt-hour with their conversion are given below the table,

Unit of energy
Joule (J) Calorie (cal) Electronvolt (eV) Kilowatt-hour (kWh)
1 0.239 6.24 × 1018 2.78 × 10-7
4.184 1 2.61 × 1018 1.16 × 10-6
1.60 × 10-19 3.82 × 10-20 1 4.45 × 10-26
3.6 × 106 8.60 × 105 2.24 × 1025 1

Heat and work

Heat is another form of energy converted into all the other forms like electrical, chemical, mechanical, kinetic, or potential by producing work. The relation between heat and work is the origin of the first law of thermodynamics. It states that if or whenever heat is obtained from work, the amount of heat produced is proportional to work spent. In another word, if heat is transferred into work, there is proportionality between the work obtained and heat disappeared.

Conversion of heat into work

Heat cannot be completely converted into work because any attempt to convert whole heat into work permanently changes the system or neighboring system. When two objects with different temperatures come together, one with a higher temperature losses heat, and the other gains it.

Types of energy conversion

The production or conversation of heat into work is going through a definite process. For example, when a liquid molecule freezes into solid yielding heat or water freezes into ice producing specific heat.

Electrical to mechanical

The electricity that passes through a circuit may produce the rotation of the armature of a motor used for lifting a weight or winding a spring. Conversely, the mechanical work done on the turbine blades of a hydroelectric power plant would generate electricity. These two examples suggest the conversion of electrical to mechanical energy or vice versa.

Chemical to electrical

Redox reaction between chemical elements zinc and copper sulfate produces a large amount of heat. The same chemical change is carried out in electrochemical cell or battery for the production of electrical energy.

What is internal energy?

In thermodynamics, every system has within itself a quantity of energy is called internal energy. It can be obtained by common observations,

  • A liquid freezes into solid yielding heat.
  • Zinc and copper sulfate in Daniell cell producing electricity.
  • Steam expands from a higher to a lower pressure yielding work or mechanical work.
  • Yellow phosphorus glows in oxygen producing light.
  • Carbon monoxide unites with oxygen to producing carbon dioxide and heat energy.

Forms of Energy

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