Electric current implies charges
in motion. The time rate of
change of electric charge passing through
a predetermined area S
is called electric current (abbreviated
as
i). Typically, this
area is the cross-sectional area of
a conductor (see Figure 2.1).
Figure 2.1 Movement of Electrons
or Ions through a Conductor of
Cross-sectional Area S.
Modeling
the Current
Mathematically,
we may define the current as
(2.1)
where
i
= intensity of the electric current
in amperes (A)
(1 A
= 1 C/s)
q
= change in electric charge t
= time interval over which the change
occurs
The
instantaneous current i,
is defined as the time rate of change
of the charge transfer at any particular
instant and is defined by
q
= change in electric charge
