Temperature gradient in a Copper Bar - Lecturer Plan
Set up the apparatus for one of the experiments described above
and proceed through the demonstration asking the following questions before or
after doing each part of the experiment as appropriate. Students would be
expected to write answers to the questions in their notebook or on specially
prepared Student handouts.
Questions for Copper rod
- Before I add water to either of the beakers what do you think the
temperature would be at various points along the rod ?
- Please draw a graph of the temperature you have estimated versus the
length along the rod.
- Please write one or two sentences explaining why you think the
temperature profile you have drawn is correct.
Present various possibilities on an overhead for the graph of
temperature versus length.
Ask for a show of hands to discover how many of the students chose a particular
solution (see overhead provided - students choose A, B or C). The number of
students responding to each could be recorded an overhead.
Now display the results of temperature versus length along the bar using the
computer.
- For those of you who did not predict this result please draw the observed
temperature on the same graph and write an explanation saying why you think
your prediction was different.
- What do you think the temperature along the rod would be immediately
after I add boiling water to one beaker and ice water to the other ?
- Please draw a graph of your prediction of the temperature along the rod
immediately after I have added boiling water to one beaker and ice water to the
other .
- Also draw a graph of the temperature along the rod for a time much
later.
- Please write one or two sentences explaining why you think the
temperature profiles you have drawn are correct.
Perform the demonstration, ensuring that the students see the response
immediately after the water has been added to both beakers. For this experiment
use the insulation to prevent heat loss to the air.
- Please draw the temperature observed immediately after I added the water
to the two beakers.
Wait until the temperatures along the rod have come to a steady state
situation.
- On the same graph as Q9 please draw the temperature observed now that
the system has come to a steady state situation.
- For those of you who did not predict this result please write an
explanation saying why you think your prediction was different.
The experiment could be repeated this time without using the insulation.
- In the demonstration just completed I placed some insulation along the
bar before I added water to the beakers. What role does the insulation perform
in this experiment?
- If I don't use the insulation and repeat the experiment adding ice
water to one beaker and boiling water to the other beaker what do you think the
temperature profile along the rod would look like this time after it has come
to a steady state situation ? Please draw your prediction.
- For those of you who did not predict this result please write an
explanation saying why you think your prediction was different.
Questions for the bar which is half copper and half stainless steel
Most of the questions above could again be asked for the demonstration
using a bar which is half copper and half stainless steel. The point in this
demonstration is to elicit student predictions about what they think happens at
the discontinuity and whether they appreciate that different materials will
conduct differently.
Transient effects
The change of temperature at a fixed point along the bar may be measured
with time. Students could be asked to predict the temperature response they
expect as the bar reaches a steady state situation.
Click here to return to the original demonstration.
Mail your comments to
p.fekete@physics.usyd.edu.au