Convection is the transfer of heat through a fluid (liquid or gas) by the movement of the fluid itself. When the fluid is heated, it expands becomes less dense and rises. The cooler fluid then sinks to take its place. This cycle creates a continuous flow known as convection current.
Thermal Properties of Matter deals with the effects of heat on different substances. It explains concepts like temperature expansion and heat capacity. The chapter includes the study of the three modes of heat transfer: conduction convection and radiation. It also covers concepts like specific heat and latent heat in materials.
Thermal convection involves the transfer of heat through the movement of the fluid itself and is achieved based on the dissimilarity of temperature within that fluid, a liquid or a gas. Thermal convection current is established, as warmer locations of the fluid become less heavy and rise above, whereas more cold regions grow denser than the rest part of the fluid and move downward inside the fluid medium.
Convection currents in water are set up when there is a temperature difference within the water. Here’s how it happens:
1. Heating: When the bottom of a container of water is heated, the water near the heat source becomes warmer. As it heats up, the water molecules move faster and spread apart, reducing the water’s density.
2. Rising of Warm Water: The less dense warm water rises to the surface.
3. Cooling at the Surface: Once the warm water hits the surface, it cools because the heat is transferred to the surroundings. The cooling densefies the water in the container.
4. Sinking of Cool Water: The denser and cooler water sinks to the bottom of the container.
5. Circulatory Flow Development: This ongoing circulation of warm rising water and sinking cool water generates convection currents that assist in the equalizing of heat over the water body.
Natural vs. Forced Convection
– Natural Convection:
– Natural convection arises based on the intrinsic density differences present in a fluid due to variations in temperature.
– As warm fluid becomes lighter and rises, the cold fluid sinks, establishing a natural convection without needing an external source.
-Example: the circulation of currents in the air, ocean circulation, or the convection of liquid in the earth
-Forced Convection
– Forced convection occurs when there is an application of an external force such as a fan or pump to stir the fluid in order to promote heat transfer.
The movement of the fluid is not because of temperature gradients but is forced upon it by means of an external agent.
Example: water being pumped through a radiator to dissipate heat or air forcibly passed over a heat sink in an electronic device.
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