Name: Introduction to First Law of Thermodynamics
Uploaded: 2019-07-19
Duration: 7 min 10 s
Description: The video defines the first law of thermodynamics and explains the relation between the total kinetic energy and the internal energy of a gas. Watch on!

Question

Explain the cyclic process with example.

Accepted Answer

In a cyclic process, the system returns to its initial state i.e its final and initial states are the same. There is no change in its state variables as it reaches its final state. Since internal energy $U$ is a state variable, there will be no change in it. Hence, for a cyclic process $∆ U = 0$ . The cyclic process of a heat engine is shown below:

A heat engine is an example of a cyclic process. The system absorbs heat from a reservoir during the isothermal process AB at a temperature $(T_{2})$ . The heat absorbed is used in work done on the environment. During the adiabatic process BC the gas expands and work is done by the gas as its temperature reaches $(T_{1})$ . It rejects heat to the sink at $(T_{1})$ during the isothermal process DC and work is done on the system. Again work is done on the system during the adiabatic process DA and it reaches temperature $(T_{2})$ . Hence, in one complete cycle, the gas again reaches the initial state at A. For the clockwise loop shown above, the net work done is positive and hence it is by the system.

Explain the cyclic process with example.

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