HOT BOX – A SIMPLE MODEL TO DEMONSTRATE THE EFFECTS OF INSULATION ON INTERNAL AND RADIANT TEMPERATURES

Anyone who has pulled on another blanket during the cold of winter will intuitively know that adding more greenhouse gas to the atmosphere will warm the planet. However, few would predict that the radiant temperature of the body-insulator system would remain the same. A simple energy balance can demonstrate this mathematically, yet many students still are unconvinced. A demonstration using a pair of cardboard boxes, 25W lights, and thermometers as well as an inexpensive IR thermometer puts students into conflict with their misconception. One box is insulated and the internal temperature of each box is recorded at 1-minute intervals by inserting a thermometer, whereas the radiant temperature is measured at a fixed distance with an IR thermometer. The trend in internal temperatures shows that, as predicted, the insulated box gets hotter and hotter faster. However, the radiant temperature of the two boxes track closely, rising and leveling off in tandem. The entire set up is inexpensive and costs less than $100. Shared use of the IR thermometer could halve the cost making this a very affordable and engaging data rich activity.