1. Heat and work are both forms of energy transfer between systems or a system and its surroundings. 2. Heat is recognized as energy transfer due solely to a temperature difference, while work is the energy transfer associated with a force acting through a distance. 3. Both heat and work are path functions that depend on the process followed between initial and final states, rather than just the initial and final thermodynamic states alone.

1. Prof. Anand Joshi
THERMODYNAMICS
Basic Concepts
Heat and Work

2. Prof. Anand Joshi
FORMS OF ENERGY
HEAT
WORK
& MASS
Heat and Work
IT’S A BOUNDRY THING….

3. Prof. Anand Joshi
Heat and Work
The Form Of Energy That Is Transferred Between Two
Systems (Or A System And Its Surroundings) By Virtue
Of A Temperature Difference
UNIT
kJ

4. Prof. Anand Joshi
Heat and Work
heat flow, heat addition, heat rejection, heat absorption, heat removal,
heat gain, heat loss, heat storage, heat generation, electrical heating,
resistance heating, frictional heating, gas heating, heat of reaction,
liberation of heat, specific heat, sensible heat, latent heat, waste heat,
body heat, process heat, heat sink, and heat source
MISUNDERSTANDING
BETWEEN
HEAT & THERMAL ENERGY
WORDS
USED
WHICH
ARE NOT
IN LINE
WITH THE
CONCET
OF HEAT
AS PER
THERMOD
YNAMICS
HEAT IS ONLY transfer of thermal energy
OR
Heat is energy in transition.
It is recognized only as
It crosses the boundary
of a system.
EXAMPLE: BAKING OF POTATO

5. Prof. Anand Joshi
Heat and Work
Kinetic Theory Vs Caloric Theory
Heat is transferred by three mechanisms:
Conduction,
Convection, And
Radiation

6. Prof. Anand Joshi
Heat and Work
Work, Like Heat, Is An Energy Interaction Between A
System And Its Surroundings.
If The Energy Crossing The Boundary Of A Closed
System Is Not Heat, It Must Be Work.
Work Is The Energy Transfer Associated With A
Force Acting Through A Distance.
Electrical Work, magnetic work, electrical
polarization work
Shaft Work, Spring Work, Elastic Solid Bars,
Stretching of a Liquid Film, Raise or to Accelerate a
Body

7. Prof. Anand Joshi
Heat and Work
1
3
2

8. Prof. Anand Joshi
Heat and Work
Work Due to a Moving Boundary
PdV Work

9. Prof. Anand Joshi
Heat and Work Path Function & Point Function
Work & Heat Both Are Path Functions
Path Functions Are Those
Which Depends On The Path Followed
All The Other Parameter Such As Temperature,
Pressure Are All Point Function Because They
Are Independent Of The Path Followed
Path Functions Have
Inexact Differentials
&
Point Function Have
Exact Differentials
Remember

10. Prof. Anand Joshi
Heat and Work
Formal Sign Convention

11. Prof. Anand Joshi
Heat and Work
SUMMARY
1. Both are recognized at the boundaries of a system as
they cross the boundaries. That is, both heat and work
are boundary phenomena.
2. Systems possess energy, but not heat or work.
3. Both are associated with a process, not a state.
Unlike properties, heat or work has no meaning at a
state.
4. Both are path functions (i.e., their magnitudes depend
on the path followed during a process as well as the end
states).

12. Prof. Anand Joshi
Heat and Work
THANK YOU