Skip to main content

Constant Pressure (Isobaric) Process

Constant Pressure or Isobaric Process - When the gas is heated at a constant pressure, its temperature and volume will increase. Since there is a change in its volume, the heat supplied is utilized in increasing the internal energy of the gas, and also for doing some external work. It may be noted that this process is governed by Charles' law.

Now consider m kg of a certain gas being heated at a constant pressure from an initial temperature T1 to a final temperature T2. This process is shown on the p-v diagram in Fig. 5.2.



We know that heat supplied to the gas at constant



Increase in internal energy,



and work done during the process or by the gas,



Notes:

(a) When the gas is cooled at constant pressure, there will be a compression. The temperature and volume will decrease during cooling and work is said to be done on the gas. In this case,

Heat rejected by the gas, 



Decrease in internal energy,



and workdone on the gas,



(b) During expansion or heating process, work is done by the gas (i.e. W1-2 is +ve); internal energy of the gas increases (i.e. dU is +ve) and heat is supplied to the gas (i.e. Q1-2 is +ve).

(c) During compression or cooling process, work is done on the gas (i.e. W1-2 is -ve); internal energy of the gas decreases (i.e. dU is —ve) and heat is rejected by the gas (i.e. Q1-2 is -ve).

Comments

  1. If work is done by the gas,it must be losing energy.Therefore the work will be -ve one.
    U=Q-W
    So how can the workdone be positive?

    ReplyDelete
    Replies
    1. Gas loses energy but the system gains that energy and pressure-volume work is done by the system to the surroundings. Any work done by the system to the surroundings is considered positive.

      Delete

Post a Comment

Popular posts from this blog

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.