Calorimetric determination of the work function

A student experiment on the calorimetric determination of the work function is described. This approach clearly demonstrates the energy transfer by electrons leaving the cathode of a vacuum tube. The changes in the temperature due to the energy transfer are detectable by measurements of the resistance of the cathode or radiation from it. Oxide-coated cathodes are more suitable for such measurements than tungsten cathodes. The calorimetric determination of the work function may become a good addition to the traditional student experiments in the field.