1).ZEROTH LAW OF THERMODYNAMICS
STATEMENT: IF TWO BODIES ARE IN THERMAL EQUILIBRIUM WITH A THIRD BODY, THEN ALL THE BODIES WILL BE IN THERMAL EQUILIBRIUM.
2).1st LAW OF THERMODYNAMICS
STATEMENT:
IF dQ amount of heat is applied to a system,then the applied heat (dQ) is equal to the sum of increase in internal energy and external work done.
Mathematically , dQ = dV+dW
3).EXTERNAL WORK DONE BY A GAS
Let us take a gas in a cylinder having a movable piston.The pressure,temperature and volume of the gas are P,T and V respectively.
Let, A= cross-sectional area of the piston.
Therefore , force exerted by the gas on the piston , F=P.A
If the piston moves through a distance dX outward,
Then work done , dW=F.dX =P.A.dX
therefore, dW =P.dV
The required energy,(P.dV ) is supplied from the KINETIC ENERGY(K.E) of the molecule .Then the K.E of the molecules decreases.
We know, K.E of gas molecule is proportional to the temperature of the gas .
Thus the temperature of the gas decreases when it expands.
4).EXTERNAL WORK DONE ON THE GAS
In this case, the temperature of the gas increases.The expression is same as the external work done on the gas.
5).ISOTHERMAL EXPANSION AND ADIABATIC CHANGE
a) The changes (Pressure & Volume) of a system in which the temperature remains constant are called isothermal change.
The changes in which the temperature of a system does not remains constant are called adiabatic change.
b) The isothermal changes are very rapid.
c) In isotheraml changes the heat of the system changes.
In adiabatic changes the heat of the system remains constant .
d) In isothermal change , PV= constant at constant temperature.
In adiabatic changes , PV=RT does not hold good.
6).SPECIFIC HEAT OF A GAS
a)Molar Specific Heat at Constant Pressure(Cp): Heat required to raise the temperature by 1 degree celsius of 1 mole of a gas at constant pressure is called molar specific heat at constant pressure(Cp).
b) Molar Specific Heat at Constant Volume(Cv): Heat required to raise the temperature by 1 degree celsius of 1 mole of a gas at constant volume is called molar specific heat at constant volume(Cv).
7).EXPRESSION FOR EXTERNAL WORK DONE IN ISOTHERMAL EXPANSION
8)WORK DONE IN A ADIABATIC EXPANSION OF A GAS.
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