Search results
Results from the WOW.Com Content Network
Von Mayer also published a numerical value for mechanical equivalent of heat in 1845 but his experimental method wasn't as convincing. Though a standardised value of 4.1860 J·cal −1 was established in the early 20th century, in the 1920s, it was ultimately realised that the constant is simply the specific heat of water, a quantity that ...
Mechanical equivalent of heat; Motive power ... for the matter of heat than water. ... method is a numerical approach for determining the values of heat capacity ...
That same year, James Prescott Joule suggested to Thomson that the true formula for Carnot's function was [20] = +, where is "the mechanical equivalent of a unit of heat", [21] now referred to as the specific heat capacity of water, approximately 771.8 foot-pounds force per degree Fahrenheit per pound (4,153 J/K/kg). [22]
The specific enthalpy of fusion (more commonly known as latent heat) of water is 333.55 kJ/kg at 0 °C: the same amount of energy is required to melt ice as to warm ice from −160 °C up to its melting point or to heat the same amount of water by about 80 °C. Of common substances, only that of ammonia is higher.
In 1845, Joule published a paper entitled The Mechanical Equivalent of Heat, in which he specified a numerical value for the amount of mechanical work required to "produce a unit of heat", based on heat production by friction in the passage of electricity through a resistor and in the rotation of a paddle in a vat of water. [33]
Using these values, Joule was able to determine the mechanical equivalent of heat. Joule estimated a mechanical equivalent of heat to be 819 ft•lbf/Btu (4.41 J/cal). The modern day definitions of heat, work, temperature, and energy all have connection to this experiment. In this arrangement of apparatus, it never happens that the process runs ...
The centigrade heat unit (CHU) is the amount of heat required to raise the temperature of one pound (0.45 kg) of water by one Celsius degree. It is equal to 1.8 Btu or 1,899 joules. [26] In 1974, this unit was "still sometimes used" in the United Kingdom as an alternative to Btu. [27]
In chemistry, heat amounts are often measured in calories. Confusingly, two units with that name, denoted "cal" or "Cal", have been commonly used to measure amounts of heat: The "small calorie" (or "gram-calorie", "cal") is exactly 4.184 J. It was originally defined so that the heat capacity of 1 gram of liquid water would be 1 cal/°C.