This document delves into the fascinating world of heat transfer, exploring the various ways in which heat energy moves from one place to another. It starts by discussing thermal expansion, the tendency of matter to expand when heated, and then delves into the three primary modes of heat transfer: ...
THERMAL EXPANSION OF SOLIDS
Increase in length of the rod depends on the material because different materials have
different arrangements of atoms.
More the length of the material, the more the expansion with the same temperature.
THERMAL EXPANSION OF LIQUIDS
Thermal expansion is the tendency of matter to change its shape, area, and volume in
response to a change in temperature.Liquids in general expand on heating.The thermal
expansion of liquids is usually higher than that of solids.
THERMAL EXPANSION OF GASES
Gas expands when it is subjected to heat.The expansion in gas is much more compared to
solids and liquids.Gases do not have a shape, so they only show volumetric expansion.The
expansion of gas is measured by keeping its pressure constant.
Modes of Heat Transfer
1. Conduction
The transfer of heat from a hot object to the cold object is called Conduction.
Heat always transfers from a body of high temperature to a body of low temperature.
Therefore, if two bodies are in contact and they have the same temperature, then there is no
net heat transfer between them.
Heat is conducted quickly through copper.
The conduction of heat takes place through a solid substance.
Atoms in any substance vibrate. On applying heat, the atoms near the hot end absorb
energy, and the intensity of vibration increases. These atoms collide with the nearby atoms
and transfer energy to the nearby atom.
Molecules in solid objects don’t "move"; they vibrate.
Plastic and wood are bad conductors of heat, while copper, steel, and aluminum are good
conductors of heat.
2. Convection
Convection can occur in liquid and gaseous substances.
Convection needs a medium.
Hotter water is lighter.
On a sea coast, the land gets heated up faster than water does. The air closer to the land
surface also becomes hot.
This hot air starts to rise up, and when this begins to happen, cold air from the sea starts to
flow to the land.Here is the transcription of the notes:
3. Radiation
The transfer of heat that takes place without a medium is called radiation.
Polished metal surfaces are good reflectors of radiation and inhibit heat energy.
Radiation of heat can transfer through a medium or without a medium.
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