What is the explanation for the mechanism of electric heat?

Answer 1

Electric heat is sometimes looked at under the heading of resistance heating. Somewhere in the heater is a resistive material through which the electric current is passed. Recall that there is always a bit of resistance in wires and such, but not much. This resistive element is selected because it resists current flow. It's a conductor, but not a very good one. When current is forced through this resistive material, it gets hot. Making current flow through a material is easy or hard. There's a fair amount of variation across materials. The specific material and its atomic or molecular structure will determine what Fermi energy levels the valence electrons are hanging out in. If these electrons can be easily accelerated by applying a voltage, the material is a conductor. The so-called conduction band is low enough that it overlaps the energy bands of the valence electrons. If the conduction band is very high above the energy of the valence bands, the material is an insulator. And there are materials that exhibit properties across an array between these extremes. It's a matter of selecting something that conducts, but well. By picking something like nichrome wire and incorporating it in an electric heater as the resistance medium, we can get that wire to generate heat by forcing electric current through it. A kitchen toaster has nichrome wire strung inside it. That's what's glowing and toasting the slice of bread. Got a hair drayer in the house? Yup, there's a nichrome wire heater inside.