Mechanical resistance model

The nail board is used to demonstrate how electrical resistance and the heating of a conductor arise. The rolling balls represent the electrons, whilst the nails represent the atomic metal lattice. The steepness of the board corresponds to the applied electrical voltage, which drives the electrons. Depending on the spacing and density of the nails, the resistance is greater or lesser. The constant collisions repeatedly slow the balls down, so that overall they move downwards at an approximately constant (drift) velocity. During these collisions, they release kinetic energy, which is converted into heat.