1. The First Law of
Thermodynamics
PREPARED BY: MANAN BHATT(17MSE003)

2. The First Law of Thermodynamics
FIRST LAW OF THERMODYNAMICS
→ CONSERVATION OF ENERGY:
 Energy Can Be Changed From One Form To Another,
But It Cannot Be Created Or Destroyed.
 The Total Amount Of Energy And Matter In The
Universe Remains Constant, Merely Changing From One
Form To Another.
 Energy Exists In Many Forms, Such As Mechanical
Energy, Heat, Light, Chemical Energy, And Electrical
Energy.
 Energy Is The Ability To Bring About Change Or To Do
Work.
 Thermodynamics Is The Study Of Energy.

3. Surroundings
The Boundary Of The System Is Arbitrarily Chosen
 The System Can Exchange Mass And Energy Through The
Boundary With The Environment.
 An Example Of “Closed System” - No Mass Flow- Is The Gas
Confined In A Cylinder. The Boundary –In This Case Real Wall- Is
Made By The Cylinder And The Piston Walls.
System

4.  An Isothermal Process Is One Where The Temperature
Does Not Change.

5.  In Order For An Isothermal Process To Take Place, We
Assume The System Is In Contact With A Heat Reservoir.
 In General, We Assume That The System Remains In
Equilibrium Throughout All Processes.
 An Adiabatic Process Is One Where There Is No Heat Flow
Into Or Out Of The System.

6.  An Isobaric Process Occurs At Constant Pressure; An
Isovolumetric One At Constant Volume.
 If The Pressure Is Constant, The Work Done Is The
Pressure Multiplied By The Change In Volume:

7.  For Processes Where The Pressure Varies, The Work Done
Is The Area Under The P-V Curve.

8.  If We Apply The First Law Of
Thermodynamics To The Human Body:
We Know That The Body Can Do Work. If The Internal
Energy Is Not To Drop, There Must Be Energy Coming
In. It Isn’t In The Form Of Heat; The Body Loses Heat
Rather Than Absorbing It.
Rather, It Is The Chemical Potential Energy Stored In
Foods.

9.  The Metabolic Rate Is The Rate At Which Internal
Energy Is Transformed In The Body.
For 65kg person

10. THANK YOU