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Energy shares the same unit of measurement with work (Joules) because the energy from the object doing work is transferred to the other objects it interacts with when work is being done. [17] The work–energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body ...
For a quasi-static adiabatic process, the change in internal energy is equal to minus the integral amount of work done by the system, so the work also depends only on the initial and final states of the process and is one and the same for every intermediate path. As a result, the work done by the system also depends on the initial and final states.
The work done on the system is defined and measured by changes in mechanical or quasi-mechanical variables external to the system. Physically, adiabatic transfer of energy as work requires the existence of adiabatic enclosures. For instance, in Joule's experiment, the initial system is a tank of water with a paddle wheel inside.
For a proof, imagine two paths 1 and 2, both going from point A to point B. The variation of energy for the particle, taking path 1 from A to B and then path 2 backwards from B to A, is 0; thus, the work is the same in path 1 and 2, i.e., the work is independent of the path followed, as long as it goes from A to B.
The work per unit of charge is defined as the movement of negligible test charge between two points, and is expressed as the difference in electric potential at those points. The work can be done, for example, by electrochemical devices (electrochemical cells) or different metals junctions [clarification needed] generating an electromotive force.
By the principle of minimum energy, there are a number of other state functions which may be defined which have the dimensions of energy and which are minimized according to the second law under certain conditions other than constant entropy. These are called thermodynamic potentials. For each such potential, the relevant fundamental equation ...
This article uses the physics sign convention for work, where positive work is work done by the system. Using this convention, by the first law of thermodynamics, The yellow area represents the work done = + where W is work, U is internal energy, and Q is heat. [1] Pressure-volume work by the closed system is defined as:
The net work equals the area inside because it is (a) the Riemann sum of work done on the substance due to expansion, minus (b) the work done to re-compress. Because the net variation in state properties during a thermodynamic cycle is zero, it forms a closed loop on a P-V diagram.