11.1: Electric Current

Describe the movement of electric charges through a medium.

Current is the rate at which charge passes through a cross sectional area of a wire.

• Electric charge moves in a circuit in response to an electric potential difference, sometimes referred to as “electromotive force” or emf ( ).

• If the current is zero in a section of wire, the net motion of charge carriers in the wire is also zero, although individual charge carriers will not have zero speed.

Although current is not a vector quantity, it does have a direction. The direction of current is associated with what would be the motion of positive charge but not with any coordinate system in space.

• The direction of conventional current is chosen to be the direction in which positive charge would move.

• In common circuits, the actual current is due to the movement of electrons (negative charge carriers).