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Q.

What is radiation,convection ?definatoin ?should be big.

Tags: electronics, science, advertising & marketing
Asked by Ayush Varun, 19 Apr '13 06:30 pm
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Answers (4)

1.

Convection: Convection is the movement of molecules within fluids (i.e. liquids, gases and rheids). It cannot take place in solids, since neither bulk current flows or significant diffusion can take place in solids. Radiation: energy that is radiated or transmitted in the form of rays or waves or particles and
It is the heat transfer by electromagnetic waves or photons. It does not need a propagating medium. The energy transferred by radiation moves at the speed of light. The heat radiated by the Sun can be exchanged between the solar surface and the Earth's surface without heating the transitional space
Answered by aflatoon, 20 Apr '13 10:08 am

 
  
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2.

That convection requires a medium is not the main difference, it is simply the most obvious aspect of what is a fundamentally different mechanism for transfering energy. Convection is the transfer of energy by movement of a medium, whereas radiation is the transfer of energy by, well, thermal radiation. Conduction also requires a medium, but, again, it is a fundamentally different mechanism than either convection or radiation; in this case it is the transfer of energy through a medium.

Unfortunately, analogies are hard but if you can visualize the particles involved, it would help. Picture the red hot iron you mentioned. On a molecular level, the material is emitting lots and lots of photons (hence why it is glowing red). The creation of these photons takes energy; energy from the heat of the iron. These photons leave the iron, pass through the environment, and eventually collide with some other object where they are absorbed and deposit their energy. This is radiative heat transfer ...more
Answered by Quest, 19 Apr '13 08:35 pm

 
  
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3.

Convection: Convection is the movement of molecules within fluids (i.e. liquids, gases and rheids). It cannot take place in solids, since neither bulk current flows or significant diffusion can take place in solids

Radiation: energy that is radiated or transmitted in the form of rays or waves or particles and
It is the heat transfer by electromagnetic waves or photons. It does not need a propagating medium. The energy transferred by radiation moves at the speed of light. The heat radiated by the Sun can be exchanged between the solar surface and the Earth's surface without heating the transitional space.
Answered by Shubham Dwivedi, 19 Apr '13 06:36 pm

 
  
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4.

Convection:
Convective heat transfer, or convection, is the transfer of heat from one place to another by the movement of fluids, a process that is essentially the transfer of heat via mass transfer. Bulk motion of fluid enhances heat transfer in many physical situations, such as (for example) between a solid surface and the fluid.[8] Convection is usually the dominant form of heat transfer in liquids and gases. Although sometimes discussed as a third method of heat transfer, convection is usually used to describe the combined effects of heat conduction within the fluid (diffusion) and heat transference by bulk fluid flow streaming.[9] The process of transport by fluid streaming is known as advection, but pure advection is a term that is generally associated only with mass transport in fluids, such as advection of pebbles in a river. In the case of heat transfer in fluids, where transport by advection in a fluid is always also accompanied by transport via heat diffusion (also known as ...more
Answered by ajooba, 19 Apr '13 06:34 pm

 
  
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