What indicates the direction of current flow in a conductor?

The direction of current flow in a conductor is indicated by the movement of electrons. In electrical terms, current is defined as the flow of electric charge, which in metallic conductors is predominantly due to the movement of negatively charged electrons. According to conventional current flow, which is an established standard, current is considered to flow from positive to negative; however, in reality, electron flow moves from negative to positive due to their negative charge.

Understanding this foundational concept helps when studying how electric circuits function, as the direction that electrons move ultimately defines the flow of current through the conductor. The other options, while they are related to electrical properties of conductors, do not directly indicate the direction of current flow. For example, the length of the conductor, its temperature, and its resistance influence the amount of current that can flow but do not provide information about the direction in which the current flows.