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How is a calorie defined in terms of heating water?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
In a thermoelectric generating system a heat source—usually fueled by coal, oil, or gas—is used within a boiler to convert water to high-pressure steam. The steam expands and turns the blades of a turbine, which turns the armature of a generator, producing electric power. A condenser converts any remaining steam to water, and a pump returns the water to the boiler.
heating In a thermoelectric generating system a heat source—usually fueled by coal, oil, or gas—is used within a boiler to convert water to high-pressure steam. The steam expands and turns the blades of a turbine, which turns the armature of a generator, producing electric power. A condenser converts any remaining steam to water, and a pump returns the water to the boiler.

A calorie is defined as the amount of heat required at a pressure of one standard atmosphere to raise the temperature of one gram of water by 1° Celsius.1

Because the specific heat of water varies slightly with temperature, the most precise definition is the "15° calorie" (or gram-calorie), which is the heat required to raise the temperature of one gram of water from 14.5° to 15.5° C. This specific measurement is equivalent to approximately 4.1855 joules. Other variations include the mean calorie, defined as 1/100 of the heat necessary to raise the temperature of one gram of water from 0° to 100° C.1