5.3) to find work done at the moving boundary of a system. Work done at the moving boundary of a system (displacement work or ‘pdV’ work)Ĭonsider an example of piston and cylinder arrangement (Fig. These include work done at the moving boundary of a system (displacement work or ‘pdV’ work), paddle-wheel work or stirrer work, shaft work, electric work, work done in moving an electric charge through an electric field, work of polarization and magnetization, work of chemical cell, work in stretching a liquid film, charging a capacitor, work done in stretching a wire, etc.ĥ.1.1.1. Different forms of work done during a processĭuring a process, there are many ways in which work can be done on or by a system. Transfer of energy in the form of work because of a flow of an electric current across the system boundaryĥ.1.1. So passing of electric current across the system boundary also constitutes transfer of energy in the form of work.įig. 5.2 then electric current crossing the system boundary is able to raise a weight with the help of a motor and pulley. Now in the above example if battery alone is considered to constitute the system as shown in Fig. Transfer of energy in the form of work because of a rotation of shaft across the system boundary So rotation of shaft across the system boundary constitutes transfer of energy in the form of work.įig. 5.1(a), we can conclude that work is being done by the system on the surroundings even there may not be any raising of a weight. Now here the battery can raise the weight with the help of an electric motor, and the sole effect external to the system is the raising of a weight. Let us now replace the fan with a pulley and weight arrangement as shown in Fig. Since no weight is being raised so it seems that no work is being done by the system on surroundings. To make it clear, the following illustration is discussed:Ĭonsider an arrangement in which the battery rotates a fan with the help of an electric motor as shown in Fig. In real life there may not be any raising of a weight but still there is work done by system on surrounding. Here raising of a weight is equivalent to a force acting through a distance. Work is said to be done by a system if the sole effect on the surroundings could be the raising of a weight. Mathematically it can be expressed asīut in thermodynamics, we define work as: Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Work is usually defined as force F acting through a displacement x, the displacement being in the direction of the force.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.This Time in History In these videos, find out what happened this month (or any month!) in history. #WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.
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