Lorentz-Drude theory :
1) Lorentz-Drude proposed that conductors like metals contain a large number of free electrons.
2) The positive ions are fixed in their locations. (The arrangement of the positive ions is called lattice).
3) The negative ions (electrons) move randomly in lattice in an open circuit.
4) When the lattice is closed the electrons are arranged in ordered motion. This
causes electric current.