Heat Engines 

Understanding Isothermal Process

   An isothermal process is a thermodynamic process in which the temperature of the system remains constant. The heat transfer into or out of the system typically must happen at such a slow rate that the thermal equilibrium is maintained.

   The internal energy of an ideal gas, however, depends solely on the temperature, so the change in internal energy during an isothermal process for an ideal gas is also 0.

Important notes about Isothermal Process

    1. Temperature is directly related to kinetic energy of the gas 

    2.  If, in the case of isothermal process, the temperature remains the same, the internal energy (thermal energy) remains the same.

     3.  Because none of the energy in converted to thermal energy it all gets converted in to work

Understanding Isobaric Process 

   An isobaric process is a thermodynamic process in which the pressure remains constant. This is usually obtained by allowed the volume to expand or contract in such a way to neutralize any pressure changes that would be caused by heat transfer.

    In an isobaric process, there are typically internal energy changes, work is done by the system, and heat is transferred, so none of the quantities in the first law of thermodynamics readily reduce to zero. However, the work at a constant pressure can be fairly easily calculated with the equation:

Understanding Isochoric Process 

     An isochoric process is a thermodynamic process in which the volume remains constant. Since the volume is constant, the system does no work and W = 0.

     This is perhaps the easiest of the thermodynamic variables to control, since it can be obtained by placing the system in a sealed container which neither expands nor contracts.

     1. Because the internal energy is the gas doesn't expand (or contracts) the volume, the work done is zero.

     2. If heat is introduced into the gas all it will do is increase the kinetic energy of the gas. 

     3. When the kinetic energy is increase, the number of collisions with the container increased, which means more pressure.

Understanding Adiabatic Process 

 An adiabatic process is one in which no heat is gained or lost by the system. The first law of thermodynamics with Q = 0 shows that all the change in internal energy is in the form of work done. This puts a constraint on the heat engine process leading to the adiabatic condition shown below. This condition can be used to derive the expression for the work done during an adiabatic process.

Definition provided by Hyperphysics 

Q = 0