Heat transfer processes

Heat transfer processes

By Tala Pawlo

The Three Mechanisms of Heat Transfer: Conduction, Convection, and Radiation.

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Radiation

Radiation is energy that originates from a source and travels at the speed of light through space. This energy is associated with an electric field and a magnetic field, and it has wave-like properties.

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Heat can be transferred by infrared radiation. Unlike conduction and convection - which need particles - infrared radiation is a type of electromagnetic radiation that involves waves.

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Conduction

Heat is thermal energy. It can be transferred from one place to another by conduction.

Metals are good conductors of heat, but non-metals and gases are usually poor conductors. Poor conductors are called insulators.

Heat energy is conducted from the hot end of an object to the cold end.

Conduction in metals

The electrons in a piece of metal can leave their atoms and move about in the metal as free electrons. The parts of the metal atoms left behind are now positively charged metal ions.

The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons.

These move through the structure of the metal, colliding with ions as they go.

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Convection

Heat can be transferred from one place to another by convection.

FluidsLiquids and gases are fluids because they can be made to flow. The particles in these fluids can move from place to place. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.

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Multiple Choice

What method of heat transfer occurs mainly in solids?

• Radiation

• conduction

• convection

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What method of heat transfer can occur in a vacuum?

• Radiation

• conduction

• convection

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What method of heat transfer occurs when particles with a lot of energy take the place of those with less?

• radiation

• conduction

• Convection

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What method of heat transfer do we see in our weather patterns?

• Radiation

• Conduction

• Convection

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Which of these methods of heat transfer does not involve particles?

• radiation

• conduction

• convection