“Sir, what is this Fermi energy? I can’t find a reasonable explanation. Which electrons have this energy and why?”
A visibly annoyed Hardik, one of my students, asked this as I started my class the other day. Hardik is one of a few undergraduate students taking a physics department elective course in IIT Kanpur, where I teach.
That copper, a garden-variety material that runs through the network of wires in our homes and lines the bottom of a few cooking utensils, has electrons at effectively at least 50,000° C was as surprising as it was worrisome for the students. And my insistent logic to prove this by assertion was not helping.
