Heat and thermodynamics-part-IV

Heat and thermodynamics-Part-IV : Heat and thermodynamics-Part-IV By R. Buvana

Heat and thermodynamics-Part-IV : Heat and thermodynamics-Part-IV 1.Thermodynamics system. 2.zeroth law of thermodynamics. 3.Heat, work and internal energy. 4.First law of thermodynamics. 5.Isothermal Process. 6.Adiabatic Process

Thermodynamic system : Thermodynamic system Thermodynamics is the study of heat, temperature and the conversion of mechanical work into heat and vice-versa. In thermodynamics, the main focus is on the macroscopic quantities of the system such as the pressure , volume, temperature, internal energy, entropy, enthalpy etc.A collection of an extremely large number of atoms or molecules confined within certain boundaries such that it has a certain values of pressure ,volume and temperature is called a thermodynamics system.

Conti… : Conti… Taking into consideration the interaction between a system and its surrounding , a system may be divided into three classes. 1.OPEN System-A system is said to be an open system if it can exchange both energy and matter with its surroundings. 2.CLOSED system-A system is said to be closed system if it can exchange only energy (not matter)with its surroundings. 3.ISOLATED system-A system is said to be isolated if it can neither exchange energy nor matter with its surroundings.

Zeroth law of thermodynamics : Zeroth law of thermodynamics Two bodies or systems in contact are said to be in thermal equilibrium if both are at the same temperature. Any isolated system is in thermodynamic equilibrium. Two systems A and B which are separately in thermal equilibrium with a third system C are also in thermal equilibrium with each other. Temperature of a system is a physical quantity, equality of which is the only condition for the thermal equilibrium of two systems or bodies in contact.

Heat, Work and Internal Energy : Heat, Work and Internal Energy Heat-Heat is the energy that is transferred between a system and its surroundings whenever there is temperature difference between the system and its surroundings. Work-Work is said to be done if a body or a system moves through a certain distance in the direction of the applied force. dw=P dV Work done on the system or gas is taken as positive. Work done by the system or gas is taken as negative.

Conti… : Conti… Internal energy(U) – Internal energy of a system is defined as the sum of the kinetic energies of the constituent particles of the system plus the sum of the potential energies of the constituent of the system. Increase in internal energy is taken as positive. Decrease in internal energy is taken as negative.

First law of thermodynamics : First law of thermodynamics The first law of thermodynamics is the law of conservation of energy. The energy entering the system in the form of heat energy is equal to the sum of the increase in the internal energy of the system and the energy leaving the system in the form of work done by the system on its surrounding's=U+W

Isothermal Process : Isothermal Process A process in which pressure and volume of the system change at constant temperature is called isothermal process. Conditions-1.There should be free exchange of heat between the system and its surroundings. All walls of container and the piston must be perfectly conducting. 2.The system should be compressed or allowed to expand very slowly so that there is a sufficient time for the exchange of heat between the system and its surroundings.

Adiabatic process : Adiabatic process A process in which pressure, volume and temperature of the system change, but there is no exchange o f heat between the system and its surroundings is called adiabatic process. Conditions-1.There should not be any exchange of heat between the system and its surroundings. All walls of the container and the piston must be perfectly insulating. 2.The system should be compressed or allowed to expand suddenly so that there is no time for the exchange of heat between the system and its surroundings.

Isochoric, isobaric and Cyclic process : Isochoric, isobaric and Cyclic process Isochoric process-A thermodynamic process that takes place at constant volume is called isochoric process. Isobaric process –A thermodynamic process that takes place at constant pressure is called isobaric process. Cyclic process-A cyclic process consists of a series of changes which return the system back to its initial state

Applications of first law of thermodynamics : Applications of first law of thermodynamics 1.Isothermal process 2.Adiabatic process 3.Isochoric process 4.Isobaric process 5.Cyclic process 6.Specific heat capacities relationship- Cp-Cv=R

Home work questions : Home work questions 1.How does internal energy of a system changes during adiabatic process? 2.is internal energy of a system changes during isothermal expansion ?If not why? 3.Can the temperature of an isolated system change?