Summary - Physics: Heat and Thermodynamics

SUMMARY

Heat is energy in transit which flows from hot object to cold object. However it is not a quantity.

Work is a process to transfer energy from one object to another object.

Temperature is a measure of hotness of the object. It determines the direction of the flow of heat.

The ideal gas law is PV = NkT or PV = μRT. The Ideal gas law holds for only at thermodynamic equilibrium. For non-equilibrium process, it is not valid.

Heat capacity is the amount of heat energy required to increase the object’s temperature by 1°C or 1K. It is denoted by S.

Specific heat capacity is the amount of heat energy required to increase the 1 kg of object’s temperature by 1°C or 1K. It is denoted by s.

Molar specific heat capacity is the amount of heat energy requires to increase the 1 mole of substance’s temperature by 1°C or 1K. It is denoted by C.

Thermal expansion is a tendency of an object to change its shape, area, and volume due to change in temperature.

Water has an anomalous behavior of expansion.

Latent heat capacity is the amount of heat energy required to change the phase of the substance.

Calorimetry is the measurement of the amount of heat energy released or absorbed by a thermodynamic system during the heating process.

Heat transfers in three different modes: conduction, convection and radiation

Stefan-Boltmann law: E = σ T⁴ and Wien’s law: λ_max T = b

Thermodynamic equilibrium: thermal, mechanical and chemical equilibrium

Thermodynamic variables : Pressure, temperature, volume, internal energy and entropy

Zeroth law of thermodynamics: If two objects are separately in thermal equilibrium with the third object, then these two are in thermal equilibrium. Temperature is a property which is the same for both the systems.

Internal energy is the sum of kinetic and potential energies of molecules in the thermodynamic system.

Joule converted mechanical energy to internal energy of the thermodynamic system

First law of thermodynamics is a statement of conservation of energy. It included heat energy of the thermodynamic system.

A quasi-static process is an infinitely slow process in which the system is always at equilibrium with the surrounding.

When the volume of the system changes, the work done W = ∫P dV

The area under the PV diagram gives the work done by the system or work done on the system.

Specific heat capacity at constant volume is always less than specific heat capacity at constant pressure.

Isothermal process: T = constant, Isobaric process: P=constant, Isochoric process: V= constant, Adiabatic process Q = 0

Work done in the isobaric process is most and work done in the adiabatic process is least

In a cyclic process, change in internal energy is zero.

The total work done in the cyclic process is given by a closed area in PV diagram

A reversible process is an ideal process.

All natural processes are irreversible.

Heat engine takes input from the hot reservoir, performs work and rejects some amount of heat energy into sink.

Carnot engine is a reversible engine. It has the highest efficiency. No real heat engine can have the efficiency of that of a Carnot engine.

A refrigerator is reverse of a Carnot engine. COP (coefficient of performance) of the practical refrigerator is always less than ideal refrigerator.