Laws of Thermodynamics

 Three laws of thermodynamics :

   1. Zeroth law of thermodynamics :This law states that when two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other.  

   2. First law of thermodynamics :This law states that the heat and mechanical work are mutually          convertible. According to this law, a definite amount of mechanical work is needed to produce a definite amount of heat and vice versa.                                                                                                                            This law is also states that the energy can neither be created nor destroyed , through it can be transformed from one form another. According to this law, the energy to the heat supplied(Q) must be balanced by the external workdone(W) plus the gain in internal energy(E) due to rise in temperature.                                          Q = W + E  

  3. Second law of thermodynamics : This law states that there is definite limit to the amount of mechanical energy, which can be obtained from a given quantity of heat energy.                                                 The second law of thermodynamics has also been stated by Kelvin-Planck as "It is impossible construct an engine working on a cyclic process, whose sole purpose is to convert heat energy in to work." According to this statement, the second law of thermodynamics is sometimes called as law of degradation of energy.