Points to be remember
1. Work and heat – are a Path Functions2. Thermodynamics properties like pressure, volume, temperature etc are point functions
3. Constant Pressure Process
The mathematical expression for displacement work can be obtained as follows:
= P (V2 – V1)
This expression shows that the area under a curve in a p-V diagram gives work done in the process.
4. Constant volume process
Consider a gas contained in a rigid vessel being heated. Since there is no change in volume, the displacement works.
W=0
5. Sign Convention of Work
Work done by the system on the surroundings is considered as positive work.
Work done on the system by the surroundings is taken as negative work.
6. Sign Convention of Heat
Heat given into a system is positive
Heat coming out of the system is negative
7. What is Homogeneous system?
The system where there is there is only one phase available. For ex-Liquid water
8. What is Heterogeneous system?
The system where there is there is more than one phase available. For ex-liquid+water
9. What is pure substance?
A substance that has a fixed chemical composition throughout is called a pure substance. For example- Water, nitrogen and carbon dioxide are all pure substances.
10. What is Perpetual Motion Machine of first kind (PMM1)?
There can be no machine which would continuously supply mechanical work without some other form of energy disappearing simultaneously.
11. What is Perpetual Motion Machine of second kind (PMM2)?
There is no heat engine that produces net work by exchanging heat only with one reservoir
12. What is absolute pressure?
The pressure relative to absolute vacuum is called the absolute pressure.
13. What is gage pressure?
The difference between the absolute pressure and the local atmospheric pressure is called the gage pressure
Pgage = Pabs –Patm
14. What is vacuum pressure?
Pressures below atmospheric pressure are called vacuum pressures
Pvac = Patm – Pabs
15. What is Statics?
It is that branch of Theory of Machines which deals with the forces and their effects while the machine parts are at rest.
16. What is the fundamental difference between a fusion weld and a solid state weld?
In a fusion weld, the metal is melted. In a solid state weld, the metal is not melted.
17. What is an autogenous weld?
An autogenous weld is a fusion weld made without the addition of filler metal.
18. What is extrusion?
Extrusion is a compression forming operation in which a work piece is forced to flow through a die opening, thus taking the cross-sectional shape of the die opening.
19. Distinguish between roll bending and roll forming?
Roll bending involves the forming of large sheet and plate metal sections into curved forms. Roll forming involves feeding a lone strip or coil through rotating rolls so that the shape of the rolls is imparted to the strip.
20. Describe in words what the Merchant equation tells us?
The Merchant equation states that the shear plane angle increases when rake angle is increased and friction angle is decreased.
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