Conventional direction of electric current
Outside a battery or an electric generator, the electric current flows
from the negative to the positive terminal.
représentation du sens du courant sur un schéma
The current direction can be indicated in a circuit diagram by placing
a red arrow on one side.
Comment: We may indicate the direction of current only in a circuit
where the electric current really flows. For example The direction of
current must not be indicated in a circuit with an open switch.
Influence of current direction on passive components
Some passive components have a different functioning if the direction
of electric current is reversed: these components are polarized.
For instance electric motors are polarized:If the current direction is
reversed then they rotate in the opposite direction.
In the opposite case we speak of non-polarized components.
Connection wires, bulbs, switches are not polarized and therefore can
be connected in any sense.
Comment: the direction of current flowing through a component can be
reversed by reversing connections of the battery or by reversing
connections of component.