### Carnot Cycle

Carnot Cycle was devised by Nicolas Leonard Sadi Carnot, to analyse the problem of the efficiency of a heat engine. In a Carnot cycle, the working substance is subjected to a cyclic operation consisting of two isothermal and two reversible adiabatic or isentropic operations. The p—v and T — s diagram of this cycle is shown in Fig. 5.7 (a) and (b) respectively. Let the engine cylinder contain m kg of air at its original condition as represented by point 1. It may be noted that

1. During isothermal expansion, as shown by 1-2 in Fig. 5.7 the heat supplied is fully absorbed by the-air and is utilized in doing external work.

Heat supplied = Workdone by the air during isothermal expansion

2. During reversible adiabatic or isentropic expansion, as shown by 2-3 in Fig. 5.7, no heat is absorbed or rejected by the air.

Decrease in internal energy = Workdone by the air during adiabatic expansion

3. During isothermal compression, as shown by 3 – 4 in Fig. 5.7, the heat is rejected and is equal to the workdone on the air.

Heat rejected = Workdone on the air during isothermal compression

Note: The expansion and compression ratio (r) must be equal, otherwise the cycle would not close.

4. During reversible adiabatic or isentropic compression, as shown by 4 –1 in Fig 5.7, no heat is absorbed or rejected by the air.

Increase in internal energy = Workdone on the air during adiabatic compression

We see from the above discussion that the decrease in internal energy during reversible adiabatic expansion 2-3 is equal to the increase in internal energy during reversible adiabatic compression 4 -1. Hence their net effect during the whole cycle is zero. We know that

Work done = Heat supplied — Heat rejected

Notes:

1. From the above equation, we see that the efficiency of Carnot's cycle increases as T1 is increased or T2 is decreased. In other words, the heat should be taken in at as high a temperature as possible, and rejected at as low a temperature as possible. It may be noted that 100% efficiency can be achieved, only, if T2 reaches absolute zero, though it is impossible to achieve in practice.

2. It may be noted that it is impossible to make an engine working on Carnot's cycle. The simple reason for the same is that the isothermal expansion 1 - 2 will have to be carried out extremely slow to ensure that the air is always at temperature T1. Similarly, the isothermal compression 3 - 4 will have to be carried out extremely slow. But reversible adiabatic expansion 2-3 and reversible adiabatic compression 4 - 1 should be carried out as quickly as possible, in order to approach ideal adiabatic conditions. We know that sudden changes in the speed  of an engine are not possible in actual practice. Moreover, it is impossible to completely eliminate friction between the various moving parts of the engine, and also heat losses due to conduction, radiation, etc. It is thus obvious, that it is impossible to realise Carnot's engine in actual practice. However, such an imaginary engine is used as the ultimate standard of comparison of all heat engines.

### Are Engineers Favourite Among Girls?

What do girls think about men who are engineers and what type of engineers are most favourite among girls? A survey was conducted by a team of aboutmech with members chosen from different countries. Each team member carried out a neutral survey in his/ her country to evaluate what females think about most of the engineers from different engineering branches. An overview of different questions asked in survey is given below:

Question: Which male engineers do you find more attractive as a husband?
Almost 50% women voted for mechanical engineers to be the most attractive husbands among other engineers. So mechanical engineers are most favourite among girls as a husband. They find them more trustworthy, intelligent, and creative. A married women from California said, “If your husband is a mechanical engineer, he will help you in everyday tasks. Because mechanical engineers are good team players and they have creative ideas about everything.”

### Best CV Format for Mechanical Engineers

Fifty percent engineers fail to grab a dream job because of basic faults in their CVs/ Resume. This article tells you about best CV format for mechanical engineers and how you are supposed to design your CV when applying for jobs. You CV is your first impression on future employer. He/ she does not know you. Your CV is the only representation of your personality. He/ she may select or reject you after first glance on your resume.
I have experienced shortlisting and interviewing candidates for different jobs. I was astonished to learn that most of the candidates simply copy paste each others CVs without any changes at all. These types of CVs are rejected immediately. I am not trying to tell you that you should avoid copying, rather i ma telling you to refrain from giving your CV to your friends.
An ideal CV consists of following portions:
Name/ Address of the applicantObjectiveEducation RecordEmployment HistoryProfessional SkillsAwards & AchievementsCo-Curricular Activities/ Inter…

### Engineering Mechanics - Introduction

The Engineering Mechanics is that branch of Engineering-science which deals with the principles of mechanics along with their applications to engineering problems. It is sub-divided into the following two main groups:

(a) Statics, and (b) Dynamics

The Statics is that branch of Engineering Mechanics which deals with the forces and their effects, while acting upon the bodies at rest.

The Dynamics is that branch of Engineering Mechanics which deals with the forces and their effects, while acting upon the bodies in motion. It is further sub-divided into the following two branches:

(i) Kinetics, and (ii) Kinematics

The Kinetics is that branch of Dynamics, which deals with the bodies in motion due to the application of forces.

The Kinematics is that branch of Dynamics which deals with the bodies in motion without taking into account the forces which are responsible for the motion.