15.2 The First Law

Every thermodynamic system possesses an interval energy U and has the capacity to do external work W which may be called the external energy. When heat energy is supplied (dQ) to a system then from the law of conservation of energy it follows that the sum total of changes in the internal and external energy of the system must equal the heat energy supplied to the system.

i.e. ........(1)

Equation (1) is the mathematical expression for the First law of Thermodynamics.

Note : (1) dU is an exact differential which just depends on the initial and the final states of the system and not on the path connecting these states.

(2) dQ and dW are in exact differentials as they are path dependent between the given initial and final states.

Index

15.1 The Zeroth Law
15.2 The First Law
15.3 Work done and Some applications of First Law
15.4 Thermodynamic Processes
15.5 Carnot Cycle
15.6 The Second Law
15.7 Entropy

  Chapter 16