Question

explain newtons law of cooling

Answer 1

yh, that deals with Heat Transfer. radiation, Convection and Conduction

Answer 2

yes can u explain me the derivation of formula

Answer 3

Newton's law of cooling states, "For a body cooling in a draft (i.e., by forced convection), the rate of heat loss is proportional to the difference in temperatures between the body and its surroundings."

Answer 4

twiddla plz?? by numerical too

Answer 5

http://www.twiddla.com/711897

Answer 6

?

Answer 7

my twiddla is acting up

Answer 8

means?

Answer 9

http://www.twiddla.com/711897

Answer 10

u r not showing der

Answer 11

http://www.twiddla.com/711903

Answer 12

u der

Answer 13

http://www.twiddla.com/709728

Answer 14

i m der

Answer 15

\[Q _{conv}=hA(T _{s}-T _{\infty})\]

Answer 16

can u explain me numerically how it comes

Answer 17

bye tlk u after 4 hrs :)

Answer 18

yh

Answer 19

thnx!

Answer 20

As EC suggests, Newton's law of cooling says that the rate of change of temperature of a body (e.g., a cup of tea) in a large environment (like sitting on the table in your kitchen) is proportional to the difference in temperature between the body and the environment.

To put it in symbols, let T be the temperature of the coffee and \( T_r \) be the temperature of the room. The rate of change of temperature we write as
\[ \frac{ \Delta T}{\Delta t} \]
where little t is time. Newton's law of cooling says this is proportional to \( -(T - T_r) \). That is, there is some positive constant k such that
\[ \frac{ \Delta T}{\Delta t} = -k(T - T_r) \]
What that means is if the tea is a lot hotter than the room; e.g., \( T_r = 20 C \) and \( T = 80 C \), then it will cool quickly, at a rate of
\[ \frac{ \Delta T}{\Delta t} = -k(T - T_r) = -k(80 - 20) = -80k \]

But later on with the tea is cooler, say T = 40 C, then the tea will cool at a rate of
\[ \frac{ \Delta T}{\Delta t} = -k(T - T_r) = -k(40 - 20) = -20k \]
which is 1/4th as slow.

Here's an example diagram showing how the temperature of the tea changes over time and converges on the temperature of the room:
In the diagram the vertical axis is temperature in C; the horizontal axis is time in minutes.

Hope that helps.

Answer 21

can u tell me how dat formula came

Answer 22

Yes, by doing an experiment. You can replicate the experiment.

Take a cup of water at 80 C or whatever; put a thermometer in it; measure and record the temperature every 1 minute.

Then draw a plot of temperature of the water vs. the change in temperature over 1 minute.

That set of data points will be close to a straight line and the slope of the line is -k where k is the constant of proportionality.

Answer 23

i need a derivation of dat formula actually..

Answer 24

Starting from general thermodynamical principles you mean? If so, maybe this gives you what you need:
http://physics.unipune.ernet.in/~phyed/23.1/23.1_teaching.pdf

Answer 25

thanQ..

Answer 26

i found tat we can even use newtons law in another way....
like if A- acceleration, Vi- initial velocity and Vo- is final velocity then we can write it as ;

by which we can write tat:
A=V/T...
sooo ..we can use it anyway