HOW HEAT MOVES?ADRIAN SILVA

CONDUCTIONConduction is a heat transfer process based on direct contact between the bodies, heat flows from the hotter to the colder object, to achieve the two objects at the same temperature. This explanation is also valid for the transmission of heat between two zones of the same solid. The physical property of materials that determines its ability to conduct heat is the thermal conductivity.

EXAMPLES1) A metal knife is heated from one end,

the other end goes into heat by conduction.

2) A cup with hot water, the cup is heated by conduction

.

CONVECTIONConvection is a form of heat transfer occurs only by means of fluid materials (liquids and gases). When a liquid or gas receiving heat, hot spots tend to rise and cool down. Hot and cold zones are mixed, the heat transmitted from one area to another, through movements called convective flows.

EXAMPLES1.The air in a balloon is heated by

convection2. The water in a pot is heated by

convection

RADIATIONRadiation is a method of heat transfer that does not require contact between the heat source and the receiver. The heat radiation is emitted by a body due to its temperature. All bodies emit energy as radiation. If it has more temperature, it emits more radiation.

EXAMPLES1. The heat of the sun comes to us by

radiation.2. The microwave heats food by radiation.

SPECIAL CASESIn many cases the three act simultaneously; but when there are solid bodies in contact, dominates the conduction, if it is fluids in contact dominates the convection and, if it is distant bodies dominates the radiation.

Example 1Pot in the kitchen

The flames heat the metal because they are in contact with the bottom and transmit heat to the pot by conduction.The pot transmits heat to the water in the bottom of the container by conduction.The hot water at the bottom rises, causing convection currents and cold water mixed with heating by convection.The walls of the hot containers emit radiation to the surroundings.

Example 2BONFIRE

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