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The mechanical equivalent of heat was a concept that had an important part in the development and acceptance of the conservation of energy and the establishment of the science of thermodynamics in the 19th century. Its independent and simultaneous discovery by James Prescott Joule and by Julius Robert von Mayer led to a priority dispute.
Gauss's law for gravity. In physics, Gauss's law for gravity, also known as Gauss's flux theorem for gravity, is a law of physics that is equivalent to Newton's law of universal gravitation. It is named after Carl Friedrich Gauss. It states that the flux (surface integral) of the gravitational field over any closed surface is proportional to ...
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 ...
e. The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium. The laws also use various parameters for thermodynamic processes, such as thermodynamic work and heat, and establish relationships ...
Joule expansion. The Joule expansion, in which a volume Vi = V0 is expanded to a volume Vf = 2V0 in a thermally isolated chamber. A free expansion of a gas can be achieved by moving the piston out faster than the fastest molecules in the gas. The Joule expansion (a subset of free expansion) is an irreversible process in thermodynamics in which ...
through a surface. In physics and engineering, heat flux or thermal flux, sometimes also referred to as heat flux density[1], heat-flow density or heat-flow rate intensity, is a flow of energy per unit area per unit time. Its SI units are watts per square metre (W/m 2). It has both a direction and a magnitude, and so it is a vector quantity.
In physics, the first law of thermodynamics is an expression of the conservation of total energy of a system. The increase of the energy of a system is equal to the sum of work done on the system and the heat added to that system: where. is the total energy of a system. is the work done on it. is the heat added to that system.
t. e. The second law of thermodynamics is a physical law based on universal empirical observation concerning heat and energy interconversions. A simple statement of the law is that heat always flows spontaneously from hotter to colder regions of matter (or 'downhill' in terms of the temperature gradient).