Stored in objects, molecules and atoms, energy takes many different forms. Whether mechanical, kinetic, thermal, chemical, radiant or nuclear, it can be converted from one form into another.
Mechanical energySum of the potential energy and kinetic energy of an object or system...
is energy stored in objects and is the sum of two other energy sources: kinetic energyThe energy of an object due to its motion.
and potential energyEnergy contained in an object or physical system that has the potential to be converted into kinetic energy...
• Kinetic energy is motion. The faster an object moves, the higher its kinetic energy. The energy of rivers (hydraulic energy) and of the wind (wind energyEnergy derived from the wind. Wind power involves converting the kinetic energy of moving air (wind) into electricity. ) is a form of kinetic energy. This energy can be converted into mechanical energy by water mills, windmills or pumps connected to turbines or into electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... when it drives a generator.
• Potential energy is the energy stored in immobile objects and the energy of position. As its name indicates, it is a potential form of energy; in other words, it only manifests itself when converted into kinetic energy. For example, when a ball is lifted, it acquires potential energy (from gravity) that only becomes apparent when it falls.
Thermal energy is simply heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter...
. It is caused by the movement of molecules and atoms within substances. Thermal energy therefore represents an object's internal kinetic energy.
In a steam engine or turbine, it is converted into mechanical energy; in a thermal powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... plant, it is converted into electricity. Thermal energy contained in the subsurface (geothermalDescribes the technology used to tap subsurface heat to produce energy... energy) can be used for heating or to generate power.
(See Feature Report: "Geothermal Energy, the Earth's Heat")
Chemical energy is energy stored in the bonds of atoms and molecules. Some chemical reactions, known as exothermic reactions, can break these bonds to release their energy.
During combustion, which is an exothermic reaction, oil, gas, coalCoal is ranked by its degree of transformation or maturity, increasing in carbon content from... and biomassIn the energy sector, biomass is defined as all organic matter of plant or animal origin... convert their chemical energy into heat — and often light. In batteries, the electrochemical reactions that occur produce electricity.
Radiant energy is energy carried by radiation. Both visible light and infrared radiation are forms of radiant energy. Both are emitted by the Sun and the filaments in electric light bulbs.
The energy of the Sun’s rays can be recovered and converted into electricity (photovoltaic solar energyEnergy produced by the photovoltaic effect. ) or heat (solar thermal power).
Nuclear energyEnergy produced in nuclear power plants. The enormous amount of heat released during fission of uranium atom nuclei is transferred to water...
is energy stored in the center of atoms, more specifically in the bonds between the particles (protons and neutrons) that make up the nucleus of an atomThe basic unit of matter and the smallest, indivisible unit of a chemical element...
. When atomic nuclei are converted by nuclear reaction, heat is released.
In nuclear power plants, the uraniumGray, very dense radioactive metal that is relatively abundant in the Earth's crust and oceans in the form of UO2... nuclei are split in a process known as fission and some of the heat released is converted into electricity.
In stars like the Sun, atomic energy is released when the nuclei combine in a process known as fusion.
Electrical energy is the energy transferred from one system to another (or stored, in the case of electrostatic energy) using electricity, which is the movement of charged particles. To be precise, electricity is an energy carrierA synonym of secondary energy (see definition). rather than a type of energy in itself, but the term "electrical energy" is commonly used in everyday speech.
Alternators and batteries are examples of systems that can provide electricity, while resistors, light bulbs and electric motors are examples of systems that receive electricity.