Energy
Energy is a quantitative property that enables work, heat transfer, and change in a system. In physics, energy exists in multiple forms and can be transformed from one form to another. The principle of energy conservation states that energy cannot be created or destroyed in an isolated system, only converted. The joule is the standard unit of energy, though kilowatt-hours and BTUs are used in practical contexts.
Common forms include kinetic energy, potential energy (gravitational and elastic), thermal energy, chemical energy, electrical energy,
Energy can be transformed by engines, generators, chemical reactions, photosynthesis, and many natural processes. The useful
Primary energy sources include fossil fuels, nuclear fission, and renewables. Electricity is a secondary energy form
Environmental and economic factors influence energy choices. Decarbonization, energy efficiency, and access to affordable energy are