12. Calorimetry, Thermal Expansion and Heat Transfer...2020/05/30  · Sol. Find amount of heat...

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Calorimetry, Thermal Expansionand Heat Transfer

By,Ritesh Agarwal, B. Tech. IIT Bombay

Heat

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

The energy that is being transferred between two bodies or between adjacent parts of a body as aresult of temperature difference is called heat. Thus, heat is a form of energy. It is energy in transitwhenever temperature differences exist.

Once it is transferred, it becomes the internal energy of the receiving body. It should be clearlyunderstood that the word "heat" is meaningful only as long as the energy is being transferred.

Thus, expressions like "heat in a body" or "heat of a body" are meaningless.

Specific Heat

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Specific heat of substance is equal to heat gain or released by that substance to raise or fall itstemperature by 1° C for a unit mass of substance.

Example

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Sol.Find amount of heat required to increases the temperature of 1 kg water by 20° C

Heat Capacity or Thermal Capacity

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Heat capacity of a body is defined as the amount of heat required to raise the temperature of that bodyby 1°.

Phase Change and Latent Heat

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Graph of Phase Change

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Calorimetry

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

The branch of thermodynamics which deals with the measurement of heat is called calorimetry.

Example

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Sol.

Thermal Expansion

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Most materials expand when their temperature is increased.Thermal expansion is like a photographic enlargement

Example

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Sol.

Variation of Time Period of Pendulum Clocks

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Example

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Sol.

Variation of Density with Temperature

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Anomalous Expansion of water

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Comparison between Different Temperature Scales

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Example

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Sol.

Heat Transfer

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Heat is energy in transit which flows due to temperature difference; from a body at higher temperatureto a body at lower temperature. This transfer of heat from one body to the other takes place throughthree routes.

(i) Conduction(ii) Convection(iii) Radiation

Conduction

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

The process of transmission of heat energy in which heat is transferred from one particle of the mediumto the other, but each particle of the medium stays at its own position is called conduction.

Thermal Resistance to Conduction

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Slabs in Parallel and Series

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

Convection

Physics by Ritesh Agarwal (B. Tech. IIT Bombay)

When heat is transferred from one point to the other through actual movement of heated particles, theprocess of heat transfer is called convection. In liquids and gases, some heat may be transportedthrough conduction. But most of the transfer of heat in them occurs through the process of convection.Convection occurs through the aid of earth’s gravity.