K.V. Lumding; K.V. Karimganj; K.V. Langjing
THERMODYNAMICS
Thermal Equilibrium:- Two systems are said to be in thermal equilibrium
with each other if they have the same temperature.
Thermo dynamical system:- An assembly of large numbers of particles
having same temperature, pressure etc is called thermo dynamical system.
Thermodynamic variables :- The variables which determine the
thermodynamic behavior of a system are called thermodynamic variables
Zeroth law of Thermodynamics :- IT states that if two system A and B are in
thermal equilibrium with a third system C , then the two system A and B are
also in thermal equilibrium with each other.
Thermodynamic Process :- A thermodynamic process is said to be taking
place , if the thermodynamic variable of the system change with time.
Types of thermodynamic Process:-
(1) Isothermal process – process taking place at constant temperature.
(2) Adiabatic process – process where there is no exchange of heat.
(3) Isochoric process – process taking place at constant volume
(4) Isobaric process –Process taking place at constant Pressure.
(5) Cyclic process:- Process where the system returns to its original state.
Equation of state : A relation between pressure, volume and temperature
for a system is called its equation of state .
Indicator diagram (P-V diagram) :- The graphical representation of the
state of a system with the help of two thermodynamical variables is called
indicator diagram of the system.
Internal energy of a gas :- It is the sum of kinetic energy and the
intermolecular potential energy of the molecules of the gas. Internal energy is
a function of temperature.
First law of Thermodynamics :- It states that if an amount of heat dQ I
added to a system , a part of heat is used in increasing its internal energy
while the remaining part of heat may be used up as the external work done
dW by the system.
161
, K.V. Lumding; K.V. Karimganj; K.V. Langjing
Mathematically dQ=dU+dW
dQ=dU+ PdV.
Work done during expansion / compression of gas:- When the volume of
gas changes from V1 to V2 , the work done is given by W= ∮ = Area
under the P -V diagram.
Thermodynamical operations are
(1) Isothermal process : A thermodynamic process that takes place at
constant temperature is called an isothermal
process.
- Equation of state for isothermal process : PV = constant.
- Work done during an isothermal process
W iso = RT loge = 2.303 RT loge
(2) Adiabatic process : A thermodynamic process that takes place in such a
manner that no heat enters or leaves the system is called adiabatic process
Equation of state for adiabatic process
(i) PV γ = constant (ii) TV γ-1 =constant (iii)
=constant
Work done during adiabatic change
( )
Wadia =
( )
Reversible process :- It is a process in which the system can be retraced to
its original state by reversing the condiditions.
Irreversible process:- It is a process in which the system cannot be retraced
to its original state by reversing the conditions.
Second law of thermodynamics:
162
THERMODYNAMICS
Thermal Equilibrium:- Two systems are said to be in thermal equilibrium
with each other if they have the same temperature.
Thermo dynamical system:- An assembly of large numbers of particles
having same temperature, pressure etc is called thermo dynamical system.
Thermodynamic variables :- The variables which determine the
thermodynamic behavior of a system are called thermodynamic variables
Zeroth law of Thermodynamics :- IT states that if two system A and B are in
thermal equilibrium with a third system C , then the two system A and B are
also in thermal equilibrium with each other.
Thermodynamic Process :- A thermodynamic process is said to be taking
place , if the thermodynamic variable of the system change with time.
Types of thermodynamic Process:-
(1) Isothermal process – process taking place at constant temperature.
(2) Adiabatic process – process where there is no exchange of heat.
(3) Isochoric process – process taking place at constant volume
(4) Isobaric process –Process taking place at constant Pressure.
(5) Cyclic process:- Process where the system returns to its original state.
Equation of state : A relation between pressure, volume and temperature
for a system is called its equation of state .
Indicator diagram (P-V diagram) :- The graphical representation of the
state of a system with the help of two thermodynamical variables is called
indicator diagram of the system.
Internal energy of a gas :- It is the sum of kinetic energy and the
intermolecular potential energy of the molecules of the gas. Internal energy is
a function of temperature.
First law of Thermodynamics :- It states that if an amount of heat dQ I
added to a system , a part of heat is used in increasing its internal energy
while the remaining part of heat may be used up as the external work done
dW by the system.
161
, K.V. Lumding; K.V. Karimganj; K.V. Langjing
Mathematically dQ=dU+dW
dQ=dU+ PdV.
Work done during expansion / compression of gas:- When the volume of
gas changes from V1 to V2 , the work done is given by W= ∮ = Area
under the P -V diagram.
Thermodynamical operations are
(1) Isothermal process : A thermodynamic process that takes place at
constant temperature is called an isothermal
process.
- Equation of state for isothermal process : PV = constant.
- Work done during an isothermal process
W iso = RT loge = 2.303 RT loge
(2) Adiabatic process : A thermodynamic process that takes place in such a
manner that no heat enters or leaves the system is called adiabatic process
Equation of state for adiabatic process
(i) PV γ = constant (ii) TV γ-1 =constant (iii)
=constant
Work done during adiabatic change
( )
Wadia =
( )
Reversible process :- It is a process in which the system can be retraced to
its original state by reversing the condiditions.
Irreversible process:- It is a process in which the system cannot be retraced
to its original state by reversing the conditions.
Second law of thermodynamics:
162
