
Physical and Electrical Background
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the inductor (for example touching it with our nger), we still have the other charge
on it, even after the inductor is taken away.
2.7 ELECTRIC CURRENT
Electric current is dened as the time rate at which electrical charges ow through
a surface (e.g., the cross section of a wire). So, it is a measure of the amount of
electrical charge Q transferred per unit time t, and its average value I is written as
I
t
=
while the instantaneous current
is given by
I
lim
i
t 0
=
=
∆→
The charges that ow represent the carriers of the
current.
With reference to Figure 2.18, n is the volume density
of carriers and S the ...