What is Voltage ?
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The voltage across an element is the
electrical pressure, measured in volts
(V),
i.e., the electromotive force (EMF),
which causes current to flow through
an electric circuit. A volt is the amount
of potential necessary to cause one
coulomb to produce one joule of work.
Electric Scalar Potential
In circuits, it is the existence
of an electric field between two points
that gives rise to the voltage difference
between them, such as across a resistor
or a capacitor. We saw that the presence
of the field E
exerts a force F
= qE
on the charge. If we attempt
to move the charge along a line, a
work will be done, or energy will
be expended in moving the charge over
a vector differential distance dl
under the influence of electric field
as shown below
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(3.1) |
Work, or energy, is measured in joules
(J).
The differential electric potential
energy dw
per unit charge is called the
differential electric potential or
differential voltage dv.
That is
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(3.2) |
The unit of V
is the volt (V),
with 1 V
= 1 J/C. The
potential difference between any two
points P1
and P2
is obtained by integrating the above
equation along any path between them.
That is
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(3.3) |
Or
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(3.4) |
Where V1
and V2
are the electric scalar potentials
at points P1
and P2,
respectively.
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