Laws of Thermodynamics

Zeroth Law and Thermal Equilibrium

This law states that if bodies A and B are each separately in thermal equilibrium with body C, then A and B are in thermal equilibrium with each other. Example.

First Law and Internal Energy

	Change in internal energy of any system	=	heat inflow	+	work done on the system
or, in symbols	dU	=	dQ	+	dW

Second law, heat engines and heat pumps

Heat Engines

No continually working heat engine can take heat from a source and convert it completely into work.

Heat Pumps

Heat cannot be transferred continually from one body to another at a higher temperature unless work is done by an external agent.