Download charge passing through a given area

ELECTRIC CURRENT
Whenever there is a net movement of
electric charge through a material, an
electric current exists.
Current = rate at which charge moves
I = q/t = charge passing through a given area
time interval
The unit for current is the ampere (A)
One ampere = one coulomb
one second
The moving charges that make up a current can
be positive or negative. However, conventional
current is defined as the direction of flow of
positive charge.
The individual charge carriers actually move
fairly slowly through a wire (on the order of
centimeters per second.)
However, the electric field moves at close to the
speed of electromagnetic radiation (3 x 108 m/s).
Direct current (DC) flows in only one
direction, while alternating current (AC) is
continuously alternating direction. Still, at
any instant the charges are moving in only
one direction.
What is the source of these charges? They
are located within the wire. When a
potential difference is applied to a circuit,
the battery supplies the energy. But the
charges are already in the wire.