Energimengder

Energimengder, or energy quantities, are physical quantities that describe the amount of energy contained in, or transferred by, a system. They are used in physics, engineering, and many applied fields to quantify energy in its various forms, such as kinetic energy, potential energy, thermal energy, chemical energy, electrical energy, and radiant energy. The standard unit is the joule (J), with larger scales using kilojoules (kJ) or megajoules (MJ).

Kinetic energy is the energy of motion and is given by KE = 1/2 m v^2 for a mass m moving at speed v. Potential energy depends on position, for example gravitational potential energy PE = m g h or elastic potential energy PE = 1/2 k x^2 for a spring. Internal or thermal energy relates to the microscopic motion and interactions of a system’s particles. Chemical energy is stored in chemical bonds, electrical energy in electric fields or circuits, and radiant energy carried by electromagnetic radiation. Nuclear energy arises from bonds in atomic nuclei.

Energy can be transferred or transformed between forms, but in an isolated system it is conserved (the first law of thermodynamics). Work and heat are two means by which energy crosses system boundaries; work changes energy, while heat is energy transfer driven by temperature differences. Measurement of energimengder can involve calorimetry, electrical metering, or spectroscopic analysis of radiation, among other methods.

Understanding energimengder is essential across physics, engineering, environmental science, and energy management, informing design, efficiency improvements, and sustainability assessments.