 Now, we start the second major topic in thermodynamics, the first law of thermodynamics. In the next few lectures, what we will be doing is the following. We will look at the history of the laws of thermodynamics. Then we will talk about the current status of the laws. Then we will see whether there is a proof for these laws. Then we will go through some details of the formalism. We will define a very important word in thermodynamics and adjective adiabatic. Then we will look at the behavior of adiabatic systems. And this behavior will be generalized as the first law and this will be the Karatheodori's form or Karatheodori's formulation of the first law of thermodynamics. Using this, we will define the thermodynamic energy E. Actually we will see that thermodynamics will define only delta E, the change in energy. Then we will consider non adiabatic processes. For non adiabatic processes, we will define the heat interaction Q. That will bring us to the final form of the first law of thermodynamics. And then we will extend this form to include the various components of delta E, the change in energy and the various components of work. And finally, we will look at one component of energy, the thermal energy U, actually the change in thermal energy delta U. Thank you.