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.
![](../../../images/bar.gif)
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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![](../../../images/equations/01Eunit/03Etopic/eq3_1.gif) |
(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
|
![](../../../images/equations/01Eunit/03Etopic/eq3_2.gif) |
(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
|
![](../../../images/equations/01Eunit/03Etopic/eq3_3.gif) |
(3.3) |
Or
|
![](../../../images/equations/01Eunit/03Etopic/eq3_4.gif) |
(3.4) |
Where V1
and V2
are the electric scalar potentials
at points P1
and P2,
respectively.
|