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Temperature and laws of thermodynamics


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Temperature and laws of thermodynamics

  1. 1. Welcome this presentation
  3. 3. 3 DEFINITION OF HEAT AND TEMPERATURE HEAT: We all know that bodies can be heated (increasing their internal energy) or cooled (losing internal energy). The energy gained or lost in these processes is heat. TEMPRATURE: Temperature is the average value of the kinetic energy of these particles. OUR PRESENTATION TROPIC IS TEMPERATURE AND LAWS OF THERMODYNAMICS
  4. 4. 4 HEAT TEMPERATURE 1. The heat lost or absorbed by a body 1.The temperature can’t lost or absorbed by a body 2. Specific heat is the property of bodies 2. Specific temperature isn’t the property of bodies 3.Heat don’t remains constant 3. Temperature remains constant
  5. 5. 5   simply states that energy can be neither created nor destroyed (conservation of energy). Thus power generation processes and energy sources actually involve conversion of energy from one form to another, rather than creation of energy from nothing. The 1st Law of Thermodyamics
  6. 6. 6 SECOND LAW OF THERMODYNAMICS  The Second Law of Thermodynamics states that "in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state."  This is also commonly referred to as entropy.  Example:  Energy changes are the driving force of the universe. The driving force of all energy change is the unstoppable tendency of energy to flow from high concentrations of energy to lower concentrations of energy.
  7. 7. 7ZEROTH LAW OF THERMODYNAMICS  The zeroth law of thermodynamics states that if two systems, A and B, are in thermal equilibrium with a third system, C, then A and B are in thermal equilibrium with each other. It is analogous to the transitive property in math (if A=C and B=C, then A=B). Another way of stating the zeroth law is that every object has a certain temperature, and when two objects are in thermal equilibrium, their temperatures are equal. It is called the "zeroth" law
  8. 8.  ΔU = Q – W where ΔU is the increase of internal energy of the system, Q is the heat entering the system, and W is the work done by the system. The differential form of the 1st Law is  dU = dQ – dW,  where dU is an exact differential, because U is a state variable, and both dQ and dW are inexact differentials, since Q and W are not state variables.
  9. 9. SECOND LAW OF THERMODYNAMICS  The entropy of an isolated system never decreases;  ΔS ≥ 0,  or, at equilibrium, S → Smax.  For a reverse Examples of irreversible (real) processes:  i. temperature equalization;  ii. mixing of gases;  iii. conversion of macroscopic (ordered) KE to thermal (random)  KE.  ble (idealized) process only,  ΔS = 0, dS = dQ/T.
  10. 10.  Zeroth Law of Thermodynamics  Two systems, separately in thermal equilibrium with a third system, are in thermal equilibrium with each other.  The property which the three systems have in common is known as temperature θ.  Thus the zeroth law may be expressed as follows:  if θ1 = θ2 and θ1 = θ3, then θ2 = θ3.
  11. 11. V2V1 P Isobaric process W = P(V2 – V1) Isothermal process V2 P V1 Calculating the work done in a reversible isothermal process requires the equation of state of the system to be known. Reversible isothermal process for an ideal gas (PV = nRT) W = ∫PdV = nRT ∫dV/V = nRT ln(V2/V1). In both cases, the work done by the system equals the shaded area under curve.
  12. 12. • THANK YOU