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The precise equivalence between calories and joules has varied over the years, but in thermochemistry and nutrition it is now generally assumed that one (small) calorie (thermochemical calorie) is equal to exactly 4.184 J, and therefore one kilocalorie (one large calorie) is 4184 J or 4.184 kJ.
The calorie is defined as the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, from a temperature of 14.5 °C, at a pressure of 1 atm. For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J .
For an overall efficiency of 20%, one watt of mechanical power is equivalent to 18 kJ/h (4.3 kcal/h). For example, a manufacturer of rowing equipment shows calories released from "burning" food as four times the actual mechanical work, plus 1,300 kJ (300 kcal) per hour, [16] which amounts to about 20% efficiency at 250 watts of mechanical output.
According to the FAO, the average minimum daily energy requirement is approximately 8,400 kilojoules (2,000 kcal) per adult and 4,200 kilojoules (1,000 kcal) a child. [3] This data is presented in kilojoules, as most countries today use the SI unit kilojoules as their primary measurement for food energy intake, [ 4 ] with the exception of the ...
1.0 kcal th (4.2 kJ) calorie (thermochemical) cal-th (g-cal-th) cal th: 1.0 ...
kilojoule: kJ kJ 1.0 ... Calorie multiples: calorie: Cal Cal The thermo-chemical calorie is the default definition. For others, see the full list. 1.0 ...
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the small calorie (gram-calorie, cal) is 4.184 J exactly. It was originally defined so that the specific heat capacity of liquid water would be 1 cal/(°C⋅g). The grand calorie (kilocalorie, kilogram-calorie, food calorie, kcal, Cal) is 1000 small calories, 4184 J exactly. It was defined so that the specific heat capacity of water would be 1 ...