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A unit of electrical energy, particularly for utility bills, is the kilowatt-hour (kWh); [3] one kilowatt-hour is equivalent to 3.6 megajoules. Electricity usage is often given in units of kilowatt-hours per year or other periods. [4] This is a measurement of average power consumption, meaning the average rate at which energy is transferred ...
This creates a limit to the amount of heat energy that can do work in a cyclic process, a limit called the available energy. Mechanical and other forms of energy can be transformed in the other direction into thermal energy without such limitations. [14] The total energy of a system can be calculated by adding up all forms of energy in the system.
In other scientific contexts, the term "calorie" and the symbol "cal" almost always refers to the small unit; the "large" unit being generally called "kilocalorie" with symbol "kcal". It is mostly used to express the amount of energy released in a chemical reaction or phase change, typically per mole of substance, as in kilocalories per mole. [32]
A kilowatt is a unit of power (rate of flow of energy per unit of time). A kilowatt-hour is a unit of energy. Kilowatt per hour would be a rate of change of power flow with time. Work is the amount of energy transferred to a system; power is the rate of delivery of energy. Energy is measured in joules, or watt-seconds.
A human in a sprint has approximately 3 kJ of kinetic energy, [20] while a cheetah in a 122 km/h (76 mph) sprint has approximately 20 kJ. [21] One watt-hour, of electricity or any other form of energy, is 3.6 kJ. megajoule The megajoule is approximately the kinetic energy of a one megagram (tonne) vehicle moving at 161 km/h (100 mph).
By Landauer's principle, the minimum amount of energy required at 25 °C to change one bit of information 3–7×10 −21 J Energy of a van der Waals interaction between atoms (0.02–0.04 eV) [11] [12] 4.1×10 −21 J The "kT" constant at 25 °C, a common rough approximation for the total thermal energy of each molecule in a system (0.03 eV) [13]
Energy conversion, process of converting energy from one form to another; Dark energy, used to explain some cosmological phenomena; Energy quality, empirical experience of the characteristics of different energy forms as they flow and transform; Energy density, amount of energy stored in a given system or region of space per unit volume, or per ...
Energy density is the amount of energy per mass or volume of food. The energy density of a food can be determined from the label by dividing the energy per serving (usually in kilojoules or food calories) by the serving size (usually in grams, milliliters or fluid ounces). An energy unit commonly used in nutritional contexts within non-metric ...