Heat is a form of energy

Heat is a form of energy. There are three different types of heat transmission, namely: conduction, convection and radiation.

Conduction. Heat may be transferred from a hotter body to a colder one by direct contact. Fast-moving molecules tend to speed up their slower neighbours on collision. We know that this method of heat transfer is called conduction.

We know that some materials are good conductors of heat and others are poor conductors. Generally speaking, metals are excellent conductors, the best conductors of electricity being also the best conductors of heat. Thus, aluminium known as a good electrical conductor is likewise a good conductor of heat. On the other hand, materials like sand, asbestos, and still air are poor conductors of heat.

Convection. In gases and liquids another process of heat transfer is very effective, namely, convection. Convection is the transfer of heat by the motion of the hot body itself carrying its heat with it. A current of liquid or gas that absorbs heat at one place and then moves to another place where it mixes with a cooler portion of the fluid and loses heat is called a convection current. Сonvection occurs only in liquids and gases.

Radiation. There is a third way by which heat travels, namely, radiation. We know the temperature of the sun is very high. We also know that, when the sun shines on the earth, the earth is warmed. The passage of heat from the sun to the earth happens by radiation. An important characteristic of radiation is that it can occur in a vacuum; it does not depend upon the presence of a substance. In addition to that, the space between the source of heat and the body to receive the heat does not rise in temperature.

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