Question

explain the cyclic process with a neat labelled PV diagram.

why is there a change in the energy of a gas when it's volume changes?​

Answer 1

Answer:

In a cyclic process, the system starts and returns to the same thermodynamic state.

The net work involved is the enclosed area on the P-V diagram. If the cycle goes clockwise, the system does work. A cyclic process is the underlying principle for an engine.

If the cycle goes counterclockwise, work is done on the system every cycle. An example of such a system is a refrigerator or air conditioner.

Example of a Cyclic Process

Expansion at constant temperature (T1).

Removal of heat at constant volume (V2).

Compression at constant temperature (T2).

Addition of heat at constant volume (V1).

We'll show that this process does work. Because the process is cyclic, there is no change in internal energy after each cycle. Therefore the net work done in each cycle equals the heat added to the system. We now analyze each of the steps in the cycle.

Step 1 - Isothermal expansion: The system does work W1 which equals the heat Q1 added to the system in the expansion, because the internal energy does not change.

Step 2 - Isochoric process: The work done is W2 = 0. Heat Q2 is removed from the system because the temperature decreases from T1 to T2.

Step 3 - Isothermal compression: The work W3 done by the system is negative, but of smaller magnitude than W1 because the area under the PV curve is less than that in step 1. The internal energy is does not change, so the heat removed is Q3 = W3.

Step 4 - Isochoric process: The reverse of step 2. W4 = 0, while heat Q4 = - Q2 is added to the system.

Cycle Summary

Because W2 and W4 = 0, the net work done is Wnet = W1 + W3

Because Q2 + Q4 =0, the net heat added is Qnet = Q1 + Q3 = Wnet

Net work done:

W1 = nRT1 ln (

V2

V1

)

W3 = nRT2 ln (

V1

V2

)

Wnet = nR (T1 - T2) ln (

V2

V1

)

Answer 2

A cyclic process can be defined as a process in which the initial and final energy are the same. It is a series of events that leave the system in the same state as when it started.

Explanation:

Cyclic Process

The initial and final internal energy of a system are equal when it goes through a cyclic process. As a result, in any cyclic process, the internal energy change is zero. Putting the first law of thermodynamics to a cyclic process, we get

                                                Δ$E= Q+W$

                                                 As, Δ$E=0$

                                                     $W=Q$

Hence, In a cyclic process, the work done by the system equals the heat absorbed by the system. The area contained in a P-V diagram represents the net work involved in a cyclic process. The structure is functional if the cycle rotates clockwise. If the anticlockwise cycle is followed, then the work is done on the system every cycle. A refrigerator or air conditioner is an example of such a system.

The internal energy of an absolute gas is calculated by:

Change in internal energy is given by:

                                               $U=\frac{nfRT}{2}$

where n is the number of moles, R is gas constant, f is the degree of freedom of gas and T is the temperature.

The change in internal energy is zero since the system returns to the same state after each cycle. The work done will be equivalent to the heat energy in this situation.