Why is heat produced in a conductor due to flow of electric current?
Energy comes in many forms: heat is mechanical motion of atoms; kinetic energy is moving mass; electrical energy is electric charge moving by electrical field forces. In a generator or battery electrons are moved from their lower energy to higher energy when there is a current in a wire the electrons move back to low level but by bump and bang into the stationary atoms. This transfers energy to the larger atoms we call heat. In special conductors called "superconductors" the electrons can move freely and smoothly and there is no "bumping" and NO heat.