Transfer of Thermal Energy

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Transfer of Thermal Energy by Mind Map: Transfer of Thermal Energy

1. Definition:

1.1. Thermal energy always flows from a region of hotter temperature to a region of lower temperature.

1.2. Only occurs when there is a difference in temperature.

2. Conduction

2.1. Definition: The transfer of thermal energy through a medium without any flow of the medium.

2.2. Metals: Good conductor of heat

2.2.1. How conduction works in metals?

2.2.2. 1. The particles at the hot end vibrate vigorously about their fixed position. The free electrons absorb thermal energy and hence gain K.E.

2.2.3. 2. The free electrons move at greater speed to the cooler end of the rod.

2.2.4. 3. As the electrons move, they collide with the cooler neighbouring particles, transferring some energy to the particles making them vibrate vigorously.

2.3. Non-metals: Good insulator of heat

2.3.1. How conduction works in non-metals?

2.3.2. 1. The particles at the hot end vibrate vigorously about their fixed position.

2.3.3. 2. They collide with neighbouring particles, making them vibrate more vigorously.

2.3.4. 3. Thermal energy has been transferred without the transfer of particles from the hotter end to the cooler end.

2.4. Conduction in liquids and gases are slower than that in solid.

2.4.1. Particles are spaced far apart -> collision between the particles are less frequent -> transfer of K.E to neighbouring particles is slower

2.5. Application of conduction

2.5.1. Cooking utensils, Double-glazed window, Winter clothings etc

3. Convection

3.1. Definition: Transfer of thermal energy by means of convection currents in a fluid (liquid/gas), due to a difference in density.

3.2. Occurs only in fluids

3.2.1. Convection does not involve transfer of thermal energy through vibration from particle to particle.

3.3. Applications of convection

3.3.1. Electric kettle, Household hot water system, Air conditioner etc

4. Radiation

4.1. Definition: Transfer of thermal energy in the form of EM waves such as infrared radiation without the aid of a medium

4.2. Emission: Results in temperature drop.

4.2.1. Dull & black surfaces are better emitter than shiny & silver surfaces.

4.3. Absorption/Radiator: Results in temperature rise

4.3.1. Dull & black surfaces are better radiator than shiny & shiny surfaces.

4.4. Factors affecting the rate of emission and absorption

4.4.1. Colour & texture of object.

4.4.2. Surface temperature.

4.4.2.1. Higher the temperature of the object's surface, higher the rate of emission of object.

4.4.3. Surface area.

4.4.3.1. Larger surface area will emit/absorb infrared radiation faster.

4.5. Application of radiation

4.5.1. Greenhouses and Vacuum flasks.