Current is defined as the flow of electrons within a conducting material or substance, such as copper electrical wire. In metallic solids, such as coper wire, the electrons flow from a low potential to a high potential. Independent of the type of charge metal carriers have, a conventional current is defined as electron flow in the same direction as positive charges. So if you have metals in which the charge of the carrier is negative, the electrons will be traveling in the opposite direction as the current. If the situation is reversed, and the charge of the carrier is positive, then the electrons will be traveling in the same direction of the current. This works well with the multiplicity of different metallic conductors available, as charges will vary depending upon the material being used. So the factor that makes the difference is the charge of the conducting material; if negative, the electron flow is opposite that of the current, if positive, the same direction.
Hello!This is because of the conventional definition of a current flow is''the flow of POSITIVE charges'' However positive charges in a conductor do not move. it is only the electrons that are mobile.