Explain how electron flow causes electric current with Lorentz- Drude theory of electrons.

According to Drude and Lorentz conductors like metals contain a large number of free electrons while the positive ions are fixed in their position. In an open circuit in a conductor electrons move randomly so net charge is zero. But in closed circuit the electrons have an ordered motion, so there is a net charge crossing through any cross section of the conductor thus causes an electric current to flow.