zeroth Law of Thermodynamics |First Law of Thermodynamics |Law of conservation of Energy |

 

-:   Thermodynamics Laws  :-

 Zeroth Law :-

            zeroth law of thermodynamics states that if two thermodynamic systems are in thermal equilibrium with third system, so we can say that they all are in thermal with each other .

         in simple words- if system X is in thermal equilibrium with system Y, and system Y is in thermal equilibrium with system Z. Then X, Y, Z will be in thermal equilibrium with each other.

        lets understand this with an example given below - 

    

              if we try to understand this in mathematical manner, so we can explain it like this -

                let         system X = system Y   ...........(1)

                             system Y = system Z   ..........(2)

                       from eq.(1) & (2), we get 

                            system X =  system Z                                                _proved

                   So in the mathematical manner, we can prove the zeroth law of thermodynamics statement.

 First Law or Law of conservation of Energy:- 

            First Law of Thermodynamics states that Energy of the Universe remains same. It neither can be created nor be destroyed, only can be convert into one form to another form.

            in other words- Any thermodynamics system in equilibrium state posses a state called internal energy(E). Between any 2 equilibrium states, the change in internal energy is equal to the difference of the heat transfer into the system and work done by the system.

            lets understand this in detail with a most suitable example- 

        here in the figure shown above, system-A is having higher energy than system-B, and heat transfer takes place between both systems. As we know that heat transfer takes place from higher temperature to lower temperature.

                now Q heat started to travel from higher temperature system-A having energyE1 towards lower temperature system-B having energyE2. But heat Q travelled a path before reaching the system-B that means some work W is done by Q heat done to reach its final destination(system-B). So some Q heat is lost in the form of work W during the travel from A to B. So we can write it as -

E2 - E1 = Q - W

                                            or      ΔE = Q - W

as   system-B is taking energy hence E2 is positive.

       system-A is giving energy hence E1 is negative.

 similarly  if work done on system ,so W will be negative.

                if work done by system, so W will be positive.

            where,    

                 E1 = available initial energy of system-A  

                 E2 = available initial energy of system-B 

                 ΔE = change in internal energy(E1-E2), 

                W = work done by system during travelling the path, to reach                            the B    = (Q - Q1)

                Q = Total heat, started to travel to reach the system-B

                Q1 = energy lost, in the path travelling from A to B.