Free Electrons

In a metallic conductor, each atom has one or more outermost electrons that are very weakly attached to the nucleus. These electrons are known as free electrons. As shown in the figure, free electrons can easily move from one atom to another within the conductor. This movement allows the transfer of negative charge throughout the conductor.

Free Electrons

Free electrons are responsible for carrying negative charges, and their motion within a conductor is what enables the flow of electricity. This property of free electrons makes metals excellent conductors of electricity.

In a conducting wire, free electrons move randomly in all directions when the wire is not connected to a power source (Figure A). This random movement does not result in any net flow of electrons, so no current flows in this state. An electric force applies to the electrons when the wire connects to the terminals of a cell (battery). Since electrons carry a negative charge, they start moving from the negative terminal (lower potential) of the cell to the positive terminal (higher potential) through the wire (Figure B).

Motion of free electrons

The movement of electrons generates an electric current in the wire. Conventional current flows in the opposite direction of electron motion, from the positive to the negative terminal. Although the electrons’ motion is irregular and random, their overall movement in one direction gives a measurable average velocity, known as drift velocity, which drives the current.

• Random motion of electrons occurs when no potential difference is applied.
• Directed motion occurs when a cell creates a potential difference, causing electrons to move and generate current.