THERMODYNAMICS -II

LIMITATION OF FIRST LAW OF THERMODYNAMICS

•It does not give information concerning feasibility of a thermodynamic proces.

whyNOT EXPLAINED BY FIRST LAW

•It tells that work obtained is equal to heat absorbed but in actual heat absorbed can not be completely converted into work.

Limitations motivating

second law

4

The second law of thermodynamics

It will arouse changes while the heat transfers from low temp.substance to high temp. one.

DIFFERENT STATEMENTS OF SECOND LAW

All spontaneous processes are thermodynamically irreversible.

.

Without the use of any external agency , heat can not by itself pass from a colder to a hotter body.

CARNOT CYCLE

State 1Thot

State 2Thot

State 4Tcold

State 3Tcold

isothermal

adiabaticadiabatic

isothermal

q=0,w=CVT

q=0,w=-CVT

w= -nRThotln(V2/V1)q=-w

w= -nRTcoldln(V4/V3)q=-w

112

The second law of thermodynamics

It will arouse changes while the heat transfers from low temp.substance to high temp. one.

119

The second law of thermodynamics

It will arouse changes while the heat transfers from low temp.substance to high temp. one.