Hello friends in this video we are going
to see a practical voltage source and
how it is different than that of ideal
voltage source so lets take a simple
circuit so the heading is practical
voltage source
so its a voltage source along with a
small resistance connected in series
which is forming a practical voltage
source so this part is a practical
voltage source
now this source I am going to connect to
a load resistance
now again circuit is closed current IL
will flow through the register which
will give rise to a voltage drop VL
across load register in this polarity
now because of this resistance which is
in series with a load some drop will be
there and that drop is given as so
voltage across this series register is
nothing but IL multiplied by R SC and
the IL value will be given as voltage
across the load resistor divided by its
value now suppose I want to plot the
graph of IL and VL
so VL versus IL which I can say a VI
characteristic of practical voltage
source
had it been given ideal voltage source
it will be simply a constant value
determined by this V but now because of
the load resistance and the resistance
connected in series with this voltage
source the voltage won't be fixed it
will be a druping in this form meaning
depend upon the value of this Rse I will
have a drop Il  multiply bt R SE so suppose I want
to write a simple equation I can say
voltage across the load register will be
equal to V minus IL  Rse so depend upon
the value of this Rse and IL I will have
some value of voltage will be dropped
across this series resistor because of
that I cannot say VL will be same as V
but it will be V minus IL RSse so there
is a small difference between ideal
voltage source and a practical voltage
source and that difference is this
series resistor so ideally this Rse
should be zero so that
I can say VL is same as V  but
practically it is not possible because
every voltage source or every battery
will have small series register
connected in series with a voltage
source so it is very difficult to avoid
this Rse practically this Rse is a small
value but it will always be that but
ideally it should be zero so henceforth
whenever we solve a problem of a source
transformation will always deal with a
practical voltage source and try to
convert that into a current source that
we will see in subsequent videos thank
you
