An experimental demonstration of Newton's law of cooling
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newtcool.ddwNewton's empirical law predicts that the rate of change of temperature will be proportional to the difference between the object's temperature and ambient. (Forced convective cooling.)
Datadisc can show the gradient at any point on the curve. Select Graph: Gradient and click on the line.
To calculate the gradient for all the data, select Data: Calculate and choose the differentiation function.
The channel for a is the one with the temperature values. A free channel will accept the new data.
We also need to calculate the difference between the temperatures and the ambient temperature (21 C)
Select the a + k function with k = 21.
The Graph: Set Axes menu command must be used now to select the right plotting parameters.
Channel 3 (temperature difference) for x and channel 1 (rate of change of temperature) for y.
Click on the option button for any channel if you want to set points to be joined etc
The plot verifies the law as a good straight line is shown. A line of best fit has been computed (see next section).
