On 26/09/2016 20:58, Alastair wrote:
On Monday, 26 September 2016 18:50:02 UTC+1, wrote:
On Monday, 26 September 2016 12:43:48 UTC+1, Alastair wrote:
Dawlish discussed the science for once and brought a point which I think is what is confusing everyone.

He wrote "'...heat *always* flows spontaneously from hotter to colder bodies, and *never* the reverse, unless external work is performed on the system'

https://en.wikipedia.org/wiki/Second_law_of_thermodynamics#Intuitive_meaning_of_ the_law"

But the sentence actually reads "FOR EXAMPLE, heat always flows spontaneously from hotter to colder bodies ...". That is not a statement of the second law, it is an example. Another example is that cold always flows from a colder to a hotter body unless external work is performed on the system e.g a refigerator.

Putting it another way hot objects always cool and cold objects always warm e.g, cup of coffeee and an ice cube. But hot cups of coffe are so common it is easy to forget about cold ice cubes. (Thanks Asha for reminding me.)

Moreover, as I have already explained, the difference in temperature between and ice cube and room temperature is much less than that between a boiling kettle and room temperature. It is only when you have a tray of ice cubes and you use the back of your hand that you can sense the cold radiation.

Pictet used a sensitive air thermometer and had cooled his ice with nitric acid when he discovered cold radiation. Count Rumford, the famous physicist, could not reproduce the experiment until he was shown how in Edinburgh.

Utter bilge. The net flow is always from warmer to cooler. Get a grip.

Idiot!

The net flow (by definition) is made up of at least two flows: a warm flow and a cold flow.

There aren't two seperate streams, one warm and one cold, somehow
battling it out for supremacy. A warm object will heat a cold object
until they reach thermal equilibrium. We can call this 'warm' radiation
but there is no distinct 'cold' radiation.
Conversely we could just flip the concept and consider that the cold
object is cooling the warm one until they reach thermal equilibrium. We
could call this 'cold' radiation but by the very act of doing so we
would have to banish any concept of 'warm' radiation.
You can think of it in one term or another, heat is just negative cold
and vice versa, the two simply can't coexist as discreet entities.


Just continue with the insults and inuendo. That is what you are good at.

Anybody who has just called someone an 'idiot' should be rather wary of
making statements like this.....

--
Col

Bolton, Lancashire
160m asl
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