Determination of Filament Work Function in Vacuum by

The objective of this experiment is to experimentally determine the work function (f) of a filament. This experiment will also demonstrate that work function is a property of the surface of the sample and has very little to do with the bulk of the sample. In this process, students will use data to determine an equation that models the relationship between temperature and resistance of a filament. Students will also construct a system for conducting research in vacuum. A Review of Work Function and Thermionic Emission: The energy required to remove an electron from the Fermi-level of a metal and free it from the influence of that metal is a property of the metal itself. This property is known as the metal’s work function (f) (Oxford Paperback Reference, 1990). Before the advent of transistors, vacuum tubes were used to amplify signals. It requires less energy to remove an electron from a vacuum tube’s filament if the work function of the filament is low. As current flows through a circuit of two dissimilar metals heat is absorbed at one junction and given up at the other. It has recently been discovered that if the metals used have low work functions this process (known as the Peltier Effect) ca