Rate of Heat Loss: Newton's Law & Factors

[franz32]

Hello everyone.

I have questions to ask.

1. What is Newton's Law of cooling?

2. The factors that affect the rate of cooling of a body are nature of a substance and temp. gradient. What are those?

3. How does each affect the cooling of a body? Are each of them varies directly with it?

 

[HallsofIvy]

"Newton's law of cooling" says that when two bodies are placed in contact, heat will flow from the body with higher temperature to the body with lower temperature at a rate proportional to the difference in the temperatures.

"2. The factors that affect the rate of cooling of a body are nature of a substance and temp. gradient. What are those?"

I'm sorry? Are you asking "what is the nature of a substance"?
"temp. gradient" is the "difference in the temperatures" above.

3. is answered in 1.

 

[franz32]

Reply to ...

Hello..

in 2, yes, what i meant is "what is the nature of a substance". thank you.

 

[Doc Al]

Originally posted by franz32
yes, what i meant is "what is the nature of a substance". thank you.

This just means that substances vary in their ability to conduct heat. (For example: silver conducts heat better than wood.) This property of a substance is called its thermal conductivity.

 

[franz32]

Graph

Hello again!

So it is meant that the 'rate of cooling of a body' is direcctly proportional to 'temp. gradient'... did I get it right? =D

And so, the graph 'temp. gradient' vs 'rate of cooling of a body' must be a line sloping upward?

How about the nature of a substance? Is the graph of it hyperbolic to the 'rate of cooling of a body'?

 

[franz32]

?...?...?

Um, something went wrong... someone did reply but I can't see it here, even I click the link...

Well, here's my problem...

How does the nature of a substance ("In rate of heat loss") affect the rate of cooling? Do they vary inversely? How does the graph looked like? =)

 

[HallsofIvy]

The "nature of a substance" is the coefficient in the proportion of heat flow to temperature distance. Specifically, it is the "heat conduction" constant for the substance. Since saying "heat flow is proportional to difference in temperature" is saying
"ΔQ= k(T₁-T_{0[/sup]) and k is the "nature of the substance", heat flow is proportional to it, not inversely proportional.}

 

[franz32]

Hello !

Hi!

Well, thank you very much, HallsOfIvy and Doc Al. =) I learned a lot! =)