<P> A flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction . Since current can be the flow of either positive or negative charges, or both, a convention is needed for the direction of current that is independent of the type of charge carriers . The direction of conventional current is arbitrarily defined as the same direction as positive charges flow . </P> <P> The consequence of this convention is that electrons, the charge carriers in metal wires and most other parts of electric circuits, flow in the opposite direction of conventional current flow in an electrical circuit . </P> <P> Since the current in a wire or component can flow in either direction, when a variable I is defined to represent that current, the direction representing positive current must be specified, usually by an arrow on the circuit schematic diagram . This is called the reference direction of current I . If the current flows in the opposite direction, the variable I has a negative value . </P> <P> When analyzing electrical circuits, the actual direction of current through a specific circuit element is usually unknown . Consequently, the reference directions of currents are often assigned arbitrarily . When the circuit is solved, a negative value for the variable means that the actual direction of current through that circuit element is opposite that of the chosen reference direction . In electronic circuits, the reference current directions are often chosen so that all currents are toward ground . This often corresponds to the actual current direction, because in many circuits the power supply voltage is positive with respect to ground . </P>

Direction of flow of electric current in a circuit
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