The mechanism of current conduction in metals is closely related to the behavior of electrons within the metal lattice structure. In a metal, such as copper or aluminum, the atoms are arranged in a crystalline lattice. These atoms consist of positively charged nuclei surrounded by a cloud of negatively charged electrons.
When a voltage (electric potential difference) is applied across the ends of a metal conductor, such as a wire, a potential gradient is established within the conductor. This potential gradient exerts an electric field that interacts with the electrons within the metal lattice. Here's how the process of current conduction in metals works:
Electron Mobility: The electrons within the metal lattice are not tightly bound to individual atoms. Instead, they are somewhat free to move within the lattice. This property is known as electron mobility. When a voltage is applied, the electric field created by the potential difference exerts a force on these free electrons.
Drift Velocity: The electrons do not flow through the metal at the speed of light; instead, they move with a much slower average velocity known as drift velocity. This is because electrons frequently collide with lattice imperfections, impurities, and other electrons as they move through the metal. These collisions contribute to the overall resistance of the metal.
Collisions and Heat Dissipation: As the free electrons move through the lattice, they collide with atoms, lattice defects, and other electrons. These collisions generate heat due to the kinetic energy transferred during collisions. This is why conducting currents through a metal wire heats it up.
Joule Heating: The heat produced by the collisions is known as Joule heating and is proportional to the square of the current passing through the wire and the resistance of the wire. This phenomenon is used in various applications, such as electric heaters and incandescent light bulbs.
Electric Current: The flow of free electrons in response to the applied voltage constitutes an electric current. The current flows in the opposite direction to the flow of electrons, as conventional current is considered to be the movement of positive charges.
It's important to note that in metals, the valence electrons (outermost electrons) of the atoms are the ones involved in conduction. These electrons are shared by many atoms in a metallic lattice and are referred to as a "sea of electrons." This shared pool of electrons is what allows metals to conduct electric current so effectively.
Overall, the mechanism of current conduction in metals relies on the movement of free electrons in response to an applied electric field, and this movement gives rise to the flow of electric current through the metal conductor.