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### Classification of Thermodynamic Cycles

The thermodynamic cycles are classified into the following groups:

1. Reversible cycle.

A process, in which some change in the reverse direction, reverses the process completely, is known as a reversible process. In a reversible. process there should not be any loss of heat due to friction, radiation or conduction, etc. A cycle will be reversible if all the processes constituting the cycle are reversible. Thus in a reversible cycle, the initial conditions are restored at the end of the cycle.

A little consideration will show, that when the operations are performed in the reversed order, the cycle draws heat from the cold body and rejects it to the hot body. This operation requires an external power to drive the mechanism according to second law of thermodynamics. A machine which operates on a reversed cycle is regarded as a "heat pump", such as a refrigerator, because it pumps heat from the cold body to the hot body. Following are the conditions for reversibility of a cycle:

1. The pressure and temperature of the working substance must not differ, appreciably, from those of the surroundings at any stage in the process.

2. All the processes, taking place in the cycle ,of operation, must be extremely slow.

3. The working parts of the engine must be friction free.

4. There should be no loss of energy during the cycle of operation.

Note: A reversible cycle should not be confused with a mechanically reversible engine. Steam engine cranks may be made to revolve in a reversed direction by mechanically altering the valve settings. But this does not reverse the cycle, on which it works. A two-stroke petrol engine may be made to revolve in reverse direction by altering the timing of ignition. But this also does not reverse the actual cycle.

2. Irreversible cycle.

A process, in which change in the reverse direction, does not reverse the process, is called irreversible process. In an irreversible process, there is a loss of heat due to friction, radiation or conduction,

In an actual practice, most of the processes are irreversible to some degree. The main causes for the irreversibility are

(i) mechanical and fluid friction,
(ii) unrestricted expansion
(iii) heat transfer with a finite temperature difference.

Moreover, friction converts the mechanical work into heat. This heat cannot supply back the same amount of mechanical work, which was consumed for its production. Thus, if there is some friction involved in the process, it becomes irreversible. A cycle will be irreversible if any of the processes, constituting the cycle, is irreversible. Thus in an irreversible cycle, the initial conditions are not restored at the end of the cycle.

Notes:

1. We have discussed the various thermodynamic processes. The processes such as constant volume, constant pressure, isothermal or constant temperature (i.e. p.v = C), adiabatic and polytropic are all reversible processes.

2. The throttling is an irreversible process.

### 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.