Transfer of Heat and Applications

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Heat is a form of . It can be transferred in three different ways. These are known as conduction, , and radiation.

Conduction is a process of heat transfer in materials. This happens by the vibrations of particles in the solid, passing on their energy.



This image shows the vibrations of atoms within a molecular structure.The atoms are connected by bonds. This allows the vibrations to be transmitted along the the structure. The greater the temperature of the object the greater the amplitude of of the particles .

Solids are good conductors compared with gases and . This is because the spacing of the particles is , making the transfer of heat by conduction easier.

Metals are the best conductors. This is because there are free in the metal, which increase the rate of conduction. Normally, metals are solid at room temperatures. An exception to this is the metal .

Liquids are poor conductors of heat, since the spacing of the particles is greater. This makes it more difficult to pass on the energy of vibrations. This movment energy is called energy.



Divers and surfers can make sure of extra insulation by wearing wetsuits. These are made of poor conductors. They wet the inside of the wetsuit with water first, to add extra . This is because water is also a poor .

Gases are even worse conductors of heat than liquids. The spacing of the is much greater in gases than liquids.


( Insulated Walls : Using 'Rockwool. This materials traps air between the fibres. )

Air is a very poor conductor of heat. Air is trapped in many good insulation materials. This makes the material an even better insulator. These materials are used for duvets, materials for outdoor wear, and loft insulation materials.

Thermal radiation is transferred as electromagnetic waves. These waves travel at the speed of . This is the way in which heat is transferred from the to Earth. It takes about eight minutes for the thermal radiation to reach Earth. We cannot see these waves, since our eyes are not sensitive to these long . When the waves strike a surface they can be absorbed or . The absorbtion of waves on the surface of an object results in ain increase of of the object.

If the surroundings are warmer then the object then the object will gain heat energy. It the object is cooler than the surroundings then the object will have an overall loss of heat energy. Dull, surfaces are best for thermal radiation. These surfaces are also the best emitters of radiation. All objects emit and absorb radiation . Light, surfaces are best at reflecting thermal radiation. These surfaces are poor absorbers of radiation.

Infrared radiation is used in thermography.



The different coloured images indicate different temperatures. Thermography used in forensic investigations. Other uses include law enforcement, firefighting, search and rescue, and medical applications.


This is an example of how solar can be used for cooking. The heat radiation is to the focus of the dish. The food is placed at this point, where it is cooked.


Solar panels for heating water are painted black to increase the amount of radiated heat absorbed, and to reduce the amount of reflected radiation. This makes the panels more . These panels also save on the of fuels and electricity for heating water. The panels cost money to install, but they will eventually save money by saving on energy bills. The time taken to recover the amount of money paid for the solar panels is called the pay- time.

If the pump is not working, then the water can circulate by the process of convection. Water when heated, and it becomes less than surrounding water. It rises because of the reduced density, and the cooler water takes its place. The cooler water then becomes heated, and it also rises. Eventually a convection is set up, and all the water becomes heated.


Forced convection is used in central heating systems in homes and at work. A pump forces the hot water through pipes and radiators.The water returns to be heated again at the . The radiators heat the surrounding air. The air then , becomes less and rises. Convection are set up in the rooms by these radiators. The radiators have a large surface , so as much contact can be made with the surrounding air as possible. This improves the of heat transfer

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