First law of thermodynamics and Cyclic process

Cyclic process:-
If a system performs the number of processes so that it comes back again to the initial state then the system the number of processes form a closed loop in a thermodynamic diagram which is called a thermodynamic cycle.

cyclic process

                                            

Sign convention of work and heat flow:-

sign convention for heat and work

                   

The first law of thermodynamics:-

The First Law of Thermodynamics states that energy can be converted from one form to another with the interaction of heat, work and internal energy, but it cannot be created nor destroyed, under any circumstances. Mathematically, this is represented as

ΔU=q+w

where

ΔU  is the total change in internal energy of a system,

q  is the heat exchanged between a system and its surroundings, and

w  is the work done by or on the system.

The algebraic sum of net heat and work interaction between a system and its surrounding in a thermodynamic cycle is zero.

                                                          ∑Q = ∑W
                           cycle        cycle
                                           ∮(Q-W)=0
                             ∮𝛅Q-𝛅W=0
►Closed cyclic integral of any point function is a zero.

             X is any point function 
                    ∮dx=0
        ∴𝛅Q-𝛅W=dx
             Q-W=Δx
   This is defined as internal energy.
  ∴𝛅Q-𝛅W=dE
  ⇒𝛅Q=𝛅W+dE
  ∴Q-W=ΔE
  ⇒Q=W+ΔE
    Q1-2-W1-2=E2-E1
    Q1-2=W1-2+E2-E1
E=u+K.E+P.E+Any other kind of energy
dE=du+d(K.E)+d(P.E)+d(..........)

 Internal energy is a point function.

Limitation of the 1st law of thermodynamics

Internal Energy:-
Internal energy is a property of system whose change in a process executed by the system equals to the difference between heat and work interactions by the system with its surroundings.

. In a thermodynamic process
       𝛅Q-𝛅W=dE
   where E is the internal energy
. The Internal energy comprises inter-molecular energy kinetic energy     potential energy of a system.

✸ For a closed or stationary system, the inter-molecular energy is the only component of internal energy and is usually denoted by the symbol "U".
                     Q1-2=W1-2+E2-E1
                     𝛅Q=𝛅W+dE
              ∮𝛅Q=∮dE+∮𝛅W

             E=u+K.E+P.E  (for stationary system K.E=0)
                    dE=du+d(K.E)+d(P.E) (small change in P.E is zero)
                    dE=du

             Q1-2=u2-u1+W1-2
                   𝛅Q=du+𝛅w
If we consider a closed system which perform only reversible displacement work that means Quasi static displacement work which is nothing but pdv work.
                   𝛅Q=du+𝛅w
             (for closed system 𝛅w=pdv)  
            𝛅Q=du+pdv

✸ The first law for a closed system in an infinitesimal process can be           written as
                 𝛅Q=du+𝛅w
✸ For a finite process between two states executed by a closed                  system.
                Q1-2=u2-u1+W1-2
✸ For a finite process for per unit mass

               
✸ For infinite
                 𝛅Q/𝛅m=du+pdv

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Zeroth law of Thermodynamics and thermodynamics properties

Zeroth Law:-
When two bodies or systems are in thermal equilibrium with a third one then they are in thermal equilibrium with each other.

Zeroth law of Thermodynamics

                         

                                        


Properties:-

• Identifiable characteristic features that describe or specify a system are known as property.
• Properties are the coordinates to describe the state of a system and therefore they are termed as state variables.
• The important conditions to be fulfilled to specify the state of a system:-

1.     The properties must be uniform throughout the system.

2.     The value of all properties should be invariant with time.

   There are two types of property:-

    → Extensive properties

      → Intensive properties

Extensive properties:-

    The properties which depend on the extent of the system and hence are directly proportional to the mass of the system are known as extensive properties.

Intensive properties:-

   The properties that do not depend upon the mass of the system and assume finite values even if the mass of the system approaches zero are known as intensive properties.

Thermodynamic equilibrium:-

   A system to be in Thermodynamic Equilibrium the property should remain variant with time and that should be uniform  within the system.

Thermodynamic equilibrium 

 #Thermal equilibrium            #Mechanical equilibrium    #Chemical equilibrium

Thermal equilibrium:-

The equilibrium states achieved by two (or more) system,         characterized by restricted values of the thermodynamic property of the system, after they have been in communication with each other through a diathermic wall. For thermal equilibrium temperature gradient should be zero.

thermal equilibrium

                      

Mechanical equilibrium:-
In the absence of any unbalance force within the system itself and also between the system and the surroundings, the system is said to be in a state of mechanical equilibrium. If an unbalanced force exits, either the system alone or both the system and the surroundings will undergo a change of state till mechanical equilibrium is attend. For mechanical equilibrium pressure gradient has to be zero.

Chemical equilibrium:-
If there is no chemical reaction or transfer of matter from one part of the system to another, such as diffusion or solution, the system is said to exit in a state of chemical equilibrium.

Temperature:-
A thermodynamic property that determines whether or not a system is in thermal equilibrium with other systems.

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Thermodynamic | Thermodynamics systems

Thermodynamics

Thermodynamics:-

Definition 1:-      Thermodynamics is the branch of physical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy), and, by extension, the relationships between all forms of energy.

 Definition 2:-       Thermodynamics is defined as a fundamental science that describes the basic law in relation to the different physical processes which involved the transfer or transformation of energy and the relation among the different physical properties of substances that are affected by such processes.

                                                                    Thermodynamics comes from two Greek words Therme and Dynamic.

Therme means Heat

Dynamic means Force

• There are two views in the study of thermodynamics:-

1. Macroscopic or Classical view
2. Microscopic or Statistical view

Macroscopic:-

      In a microscopic view, attention is made to a certain quantity of matter without consideration of the events occurring at the molecular level.

Microscopic:-

    In a microscopic view, the properties of matter are studied at the molecular level.

System:-

    A system is defined as a quantity of matter upon which attention is made in the analysis of a problem and this is always bounded by a boundary.

Systems

                                       

     There are generally three types of systems:-

1. Control mass system (closed system )

2. Control volume system (open system)

3.  Isolated system

1. Control mass system:-

    A system of fixed mass with first identity is known as a control mass system. There is only energy transfer but no mass transfer across the system boundary.

Closed system

Closed system

                            

2. Control volume system:-

   A system in which matter crosses the system boundary and remains fixed without any change in the volume of the system is known as the control volume system.

Open System

Open System

                            

3. Isolated system:-

  An isolated system is one in which there is neither interaction of mass nor energy between the system and the surroundings.

Isolated System

                                     

Adiabatic System:-
An adiabatic system is one that is thermally insulated from its surroundings. It can,
however, exchange work with its surroundings. If it does not, it becomes an isolated system. 

Homogeneous System:-
A system that consists of a single phase is termed a homogeneous system. Examples :
A mixture of air and water vapor, water plus nitric acid, and octane plus heptane.

Heterogeneous System:-
A system that consists of two or more phases is called a heterogeneous system. Examples :
Water plus steam, ice plus water, and water plus oil.                      

Boundary:-

  The boundary is a solid boundary or may not be a solid boundary and sometimes boundary may be an imaginary boundary. Which separates the system and its surrounding area known as the boundary of the system.

Boundary

                                 

Surrounding:-
  Everything external to the system as separated by the system boundary is known as the surrounding.

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