## atjari 3 years ago Plssssss help.

1. atjari

|dw:1331452540087:dw|

2. atjari

3. atjari

pls see the attachment for the question

4. Mani_Jha

Efficiency is the ratio of the energy given to the system, to the net work done by the system. Now, can you tell me how will you find the net work done by the system from the graph?

5. SidharthSahoo

Hey Mani come to chat box

6. atjari

Net work=P2(V1-V2)-delta U

7. Mani_Jha

Well, actually the net work done by the system in a cyclic process is the area of the closed graph. Lets see how much work we have done to the system From 1 to 2, the work done is P2(V2-V1) From 2 to 3, no work is done From 3 to 1, the work done is (P3V2-P2V1)/(gamma -1) The work done by us is the sum of all the above. The work done by the gas is : W(1,2)+W(2,3)-W(3,1) Find the ratios of work done by gas, to work done by us. That should be the efficiency.

8. atjari

Can u explain hw u got (P3V2-P2V1)/(gamma -1) for 3to1

9. Mani_Jha

The work done by a gas in an adiabatic process is : $(Pinitial \times Vinital-Pfinal \times Vfinal)/(\gamma-1)$ You can also prove this. Now, is it ok?

10. atjari

Ha k. Thanx a lot.

11. atjari

|dw:1331455348197:dw|

12. atjari

@Mani Jha

13. Mani_Jha

Hey, let me calculate and see. I will post as soon as I do this

14. atjari

Ha k. Thanx.