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Making Energy Visible

10. November 2017

Making Energy Visible - Thermal Imaging Cameras as a Teaching Tool

Developing a deep understanding of energy is difficult for many students, and energy conservation is especially challenging for them. This difficulty can be attributed to students’ everyday experiences. In everyday life, processes end more or less quickly, and energy seems to disappear. For example, when a stone falls to the ground, the energy that the stone just had, due to its movement, seems to have simply disappeared. The principle of energy conservation, however, says that energy cannot simply disappear. So where has the energy gone?
We know that it has been converted into thermal energy in the environment – the temperature of the environment has increased, but this temperature increase is short-lived and strongly localized. Thus, it is hard to measure and observe temperature increase in classrooms using traditional thermometers. Consequently, the fact that the motion energy of the stone has not disappeared, but instead been converted into thermal energy of the environment, is difficult for many students to accept.  In the end, teachers often have no choice but to simply ask students to believe that these short-lived temperature changes occur without seeing evidence for them.  This is not a good representation of how science is done.

With the aid of thermal imaging cameras, otherwise undetectable evidence of everyday thermal energy conversions can be made visible. All objects radiate heat, depending on the temperature of the object, and the radiation produced by small temperature variations can be measured by the thermal imaging camera and translated into a color for each pixel in a digital image. These digital thermal images can illustrate, for example, whether a house is properly insulated and how our skin gets “visibly” cooler if we touch an ice cube.

If the stone mentioned earlier is dropped on a piece of wood or fleece, a thermal imaging camera can reveal a clear temperature change on the surface where the stone landed. Whereas a regular thermometer must be very precisely positioned and very sensitive to detect the small, short-lived temperature increase of the surface, the thermal imaging camera makes this brief temperature change much easier to see.  Further, the picture or video can be easily stored and used to document the observation, to discuss the experiment, and to serve as a point of reference for future lessons.

The impact of a stone can be documented using a thermal imaging camera
An energy transformation takes place confirming our perception of effort in this chair position

Thermal cameras can also provide evidence of unseen energy conversions that occur within the human body. Using a thermal imaging camera, it can be shown that when a student sits in a chair position supported only by the wall, his thigh muscle gets warm.  That is, an energy conversion takes place in the students’ muscles. Thermal cameras can confirm our perception of effort in this position indeed requires energy conversion, even though the student is not doing work as defined by the physical concept – another (apparent) contradiction which is typically difficult to reconcile with students experiences.

Thermal imaging cameras are no longer expensive. Today, thermal cameras are available as attachments for smartphones or tablets, and they appearing in more and more school inventories. This newly-inexpensive tool opens up new possibilities for teaching the energy concept. By showing direct evidence of previously unseen thermal energy conversions, students have more opportunities to deepen their understanding of energy and to use energy ideas to explain real-world events.