➔ Tephigram is the name of temperature entropy diagram
➔ PV graph in a adiabatic change is called Isentropic.
➔ Entropy of a system is an index of “unavailable energy”.
➔ When gas is expanded, work is done by the gas on surroundings.
➔ The size of “Kelvin degree” is equal to “Centigrade”.
➔ The efficiency of a carnot engine increases by raising the temperature of the source.
➔ Work done per cycle is given by the area enclosed in the indicator diagram.
➔ Conversion of heat energy into electrical energy can be made by “Thermocouple”.
➔ f(P,V,T) =0 exists for an equilibrium state and is called equation of state.
➔ The area of cycle of T-S diagram gives the “available thermal energy for useful work” in a reversible process.
➔ Uses of TS diagram:
a) used in meteorology b) check efficiency of heat engine c) useful in predicting defects of performance of engine d) to obtain work value of fuel used.
➔ Change in entropy of universe due to free expansion is
∆S = nR log e(Vf/Vi)
➔ Loss of available of energy = To.dS where ‘To’ is lowest available temperature in system.
➔ In order to maintain a body in an isothermal condition, heat has to be either supplied or withdrawn.
➔ When a gas expands adiabatically, the temperature decreases.
➔ When a gas is compressed, the temperature increases because work is done on the gas.
➔ The work done in an adiabatic change in a particular gas depends upon only change in temperature.
➔ In an adiabatic compression, the decrease in volume is associated with increase in temperature & increase in pressure.
➔ For an isothermal expansion of a perfect gas, the value of dP/P is equal to -dV/V.
➔ Change in entropy of universe due to free expansion is
∆S = nR log e(Vf/Vi)
➔ Loss of available of energy = To.dS where ‘To’ is lowest available temperature in system.
➔ In order to maintain a body in an isothermal condition, heat has to be either supplied or withdrawn.
➔ When a gas expands adiabatically, the temperature decreases.
➔ When a gas is compressed, the temperature increases because work is done on the gas.
➔ The work done in an adiabatic change in a particular gas depends upon only change in temperature.
➔ In an adiabatic compression, the decrease in volume is associated with increase in temperature & increase in pressure.
➔ For an isothermal expansion of a perfect gas, the value of dP/P is equal to -dV/V.
➔For an adiabatic expansion of a perfect gas, the value dP/P is equal to -š¯›¾dV/V.
➔ A reversible process is always “quasi-static”, but every quasi-static process need not be a reversible process.
➔ For reversible cycle: ∆P = ∆V = ∆T = ∆U = ∆H
➔ dW = PdV is only applicable to reversible process.
➔ In case of “irreversible processes”, dW is not equal to PdV;
➔ For reversible cycle: ∆P = ∆V = ∆T = ∆U = ∆H
➔ dW = PdV is only applicable to reversible process.
➔ In case of “irreversible processes”, dW is not equal to PdV;
➔For free expansion, dW=0
➔For free expansion, dV=0, the work may be zero (in case of PV work)
➔For free expansion, dV=0, the work may be zero (in case of PV work)
➔ Work and heat are path functions.
➔ Work is not a thermodynamic property as it is not a state function and it is not a exact differential.
➔ Both thermodynamic and temperature scales use a single reference temperature i.e triple point of water.
➔ dW = PdV is only applicable to reversible process.
➔ Work is not a thermodynamic property as it is not a state function and it is not a exact differential.
➔ Both thermodynamic and temperature scales use a single reference temperature i.e triple point of water.
➔ dW = PdV is only applicable to reversible process.
➔ In case of “irreversible processes”, dW is not equal to PdV;
