## atjari Group Title Plssssss help. 2 years ago 2 years ago

1. atjari Group Title

|dw:1331452540087:dw|

2. atjari Group Title

3. atjari Group Title

pls see the attachment for the question

4. Mani_Jha Group Title

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 Group Title

Hey Mani come to chat box

6. atjari Group Title

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

7. Mani_Jha Group Title

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 Group Title

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

9. Mani_Jha Group Title

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 Group Title

Ha k. Thanx a lot.

11. atjari Group Title

|dw:1331455348197:dw|

12. atjari Group Title

@Mani Jha

13. Mani_Jha Group Title

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

14. atjari Group Title

Ha k. Thanx.