Classroom Activity for 11-14
What the Activity is for
The purpose of this demonstration is to show the build-up of convection currents of warm air in a room.
What to Prepare
- a model room
- a data logger plus three temperature probes
- a data projector plus large display
The model room can be made from a shoebox with the front cut away and covered with acetate film. The
ceiling and rear wall of the box should be covered with thermochromic film. The room contains a
heater mounted next to one end wall that is made from a resistor of a few ohms (sized to match the room – for a shoebox say 1 ohm, 10 watt). Finally, make small holes in the roof and both end walls to accept three temperature probes.
What Happens During this Activity
Turn on the heater (two to four volt across the resistor usually works well) and wait until the thermochromic film shows the spread of warmth – usually about five minutes. You'll need to practice the demonstration first, and possibly alter the value of the resistor and the power supply settings.
Turn off the heater and lift off the roof of the model room to show the pattern of the temperatures inside. It may be worth capturing this pattern by taking a photograph with a digital camera for future reference.
Then replace the now cool roof over the cool heater and repeat the warming, this time with three temperature probes installed (make sure that the class is involved in choosing where these are placed, so exploring their understanding of what they've just seen). Before the second demonstration, ask the class to predict the shapes of the temperature-time curves as well as the relative values.