Q. What is the main method of heat transfer in solids?

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    Basics Conduction
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Discussion Overview

The discussion revolves around the methods of heat transfer in solids, liquids, and gases, with a focus on conduction, convection, and radiation. Participants explore the definitions and implications of these processes, particularly in the context of heating devices like radiators.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that heat can be transferred by conduction only in solids, while others challenge this by stating that conduction also occurs in liquids and gases, albeit less efficiently.
  • There is a question about the terminology used for heating devices, particularly whether 'radiator' is an appropriate term given that it primarily heats by convection rather than radiation.
  • Some participants propose that the warm air trapped between layers of clothing or wetsuits conducts and radiates heat to adjacent layers.
  • One participant suggests that while radiators may heat rooms by convection, they primarily heat individuals in front of them through radiation.
  • Concerns are raised about the authoritative tone of certain educational resources, with suggestions for alternative materials that may present the information more accurately.
  • A participant explicitly states that the claim from a cited source regarding conduction being limited to solids is incorrect.

Areas of Agreement / Disagreement

Participants express disagreement regarding the efficiency of conduction in fluids and the appropriateness of the term 'radiator.' There is no consensus on the definitions and implications of heat transfer methods, and the discussion remains unresolved.

Contextual Notes

Some statements made by participants reflect a reliance on specific educational resources, which may present simplified or authoritative views that do not encompass the full complexity of heat transfer phenomena.

Cliff Hanley
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From gcsescience.com;

"Heat can be transferred by conduction only in solids."

Q. Doesn't conduction take place directly prior to convection (when a radiator heats up a room)? If my cold hand came into contact with the warm radiator this would cause conduction; why isn't it the same for the cold air coming into contact with the warm radiator?

Q. Is it the case that 'radiator' isn't the most sensible term for the heating device in question given that, although it does radiate heat, it mainly heats up the room by causing convection?
 
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Yes, there is conduction in liquids and gasses (together known as fluids). It is not very efficient though. If you can engineer your system to prevent fluid circulation (think: layers of clothing, diving wetsuits), you end up with heat transfer only through radiation and conduction.
There's a bit more on that here and on the following page:
http://www.spaceflight.esa.int/impress/text/education/Heat Transfer/Conduction 01.html

The site you refer to appears to be using the simplifying approach of 'if it's small, ignore it completely'.
It's not the best approach, IMO, as it prevents one from seeing the actual physics (like how you've observed with the radiator), and seems to be geared for drilling in answers to exam questions rather than teaching physics.
Looking at your other threads, the site likes to speak authoritatively in that manner. Perhaps you'd be better off with a different resource for learning physics. You may still want to use that site in order to know what sort of answers the exams might expect, though.

Cliff Hanley said:
Q. Is it the case that 'radiator' isn't the most sensible term for the heating device in question given that, although it does radiate heat, it mainly heats up the room by causing convection?
Yeah, 'radiator' does not predominantly radiate. I think the name comes from the common-sense observation that 'heat radiates outward from it', rather than the actual physics of heating.
 
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“If you can engineer your system to prevent fluid circulation (think: layers of clothing, diving wetsuits), you end up with heat transfer only through radiation and conduction.”

Q. So the warm air trapped between the layers conducts and radiates heat to the layer beneath and above?

“Perhaps you'd be better off with a different resource for learning physics. You may still want to use that site in order to know what sort of answers the exams might expect, though.”

Yes, thanks, I’m considering this already.“Yeah, 'radiator' does not predominantly radiate.”So there is conduction (but a small amount) between the surface of the radiator and the molecules of air coming into contact with it? What predominately heats the air to start it rising, ie, starts the convection process; radiation or conduction?
 
Cliff Hanley said:

Q. Is it the case that 'radiator' isn't the most sensible term for the heating device in question given that, although it does radiate heat, it mainly heats up the room by causing convection?
It may heat the room by convection but it heats the persons in front of it mainly by radiation.
They are pretty bad at heating the room unless they are combined with a fan to circulate the air.
And then, the layer of air right next to the hot element is heated by conduction.

Maybe these statements are useful by making you think about their validity but you should not take them too seriously, especially if they are just about words.
 
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Bandersnatch said:
Looking at your other threads, the site likes to speak authoritatively in that manner. Perhaps you'd be better off with a different resource for learning physics. You may still want to use that site in order to know what sort of answers the exams might expect, though.

BBC Bitesize is usually quite good at avoiding over-complication without simply ignoring reality: http://www.bbc.co.uk/bitesize/standard/physics/energy_matters/heat_in_the_home/revision/1/ "Conduction of heat energy takes place mainly in solids... In liquids and gases (fluids) heat energy is transferred mainly by a process called convection."
 
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Cliff Hanley said:
From gcsescience.com;

"Heat can be transferred by conduction only in solids."


This is not correct.

Chet
 
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Cliff Hanley said:
From gcsescience.com;

Based on what you've posted from this site so far, I'd suggest that you stop using it. :-p
 
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