# Mechanical equivalent of heat

## Definitions

• Webster's Revised Unabridged Dictionary
• Mechanical equivalent of heat (Physics) originally defined as the number of units of work which the unit of heat can perform, equivalent to the mechanical energy which must be expended to raise the temperature of a pound of water one degree Fahrenheit; later this value was defined as one British thermal unitB.t.u). Its value was found by Joule to be 772 foot pounds; later measurements give the value as 777.65 foot-pounds, equivalent to 107.5 kg-meters. This value was originally called Joule's equivalent, but the modern Joule is defined differently, being 107 ergs. The B.t.u. is now given as 1,054.35 absolute Joules, and therefore 1 calorie (the amount of heat needed to raise one gram of water one degree centigrade) is equivalent to 4.186 Joules.
• Mechanical equivalent of heat See under Equivalent.
• ***
Chambers's Twentieth Century Dictionary
• Mechanical equivalent of heat the relation between heat and work—viz. the amount of molecular energy required to produce one heat-unit
• ***

## Etymology

Chambers's Twentieth Century Dictionary
A.S. hǽto, heat, hát, hot; Ger. hitze.

## Usage

### In literature:

Joule worked out the mechanical equivalent of heat by means of his now famous experiment of churning water.
"Q. E. D., or New Light on the Doctrine of Creation" by George McCready Price
The acceptance of this view led to the highly important inquiry, What is the equivalent relation between mechanical force and heat?
"The Atlantic Monthly, Vol. 13, No. 78, April, 1864" by Various
Thus the mechanical equivalent of heat is a fixed and definite quantity.
"Essays Towards a Theory of Knowledge" by Alexander Philip
He goes fully through the calculation of the mechanical equivalent of heat.
"Fragments of science, V. 1-2" by John Tyndall
Heat, Mechanical equivalent of, 23.
"God and the World" by Arthur W. Robinson
C. is called the mechanical equivalent of heat.
"Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3" by Various
This is known as the mechanical equivalent of heat, or Joule's equivalent.
"The New Gresham Encyclopedia" by Various
The mechanical equivalent of the heat generated in the boiler is easily calculated when the conditions of working are known.
"A History of the Growth of the Steam-Engine" by Robert H. Thurston
Mechanical equivalent of heat and heat equivalent of fuels and efficiency of engines.
"Physics" by Willis Eugene Tower
***