currents and voltages
are alternating currents and voltages ?
Direct voltages and currents
A DC voltage generator (such as a battery) provides a constant voltage
in value but also in sign.
A DC voltage generator produces a current that always flows in the same
direction (from negative terminal to positive terminal )
An alternator is a generator that provides an alternating voltage and
an alternating current.
When a generator operates its magnet (or electromagnet) is rotating:
the magnetic north pole approaches and then moves away from the coil
and then it is the turn the south pole. This succession of approaches
and moving away of the two poles causes a succession of positive and
negative voltage at the terminals of coil.
The voltage supplied by a alternator is called alternative because it
is alternately positive and negative.
An alternator's voltage is alternately positive and negative because
of its terminals that also change sign.
The electric current that flows from negative terminal to positive
terminal changes its direction when these terminals change their sign:
The current flows alternately in one direction and then in another.