hello friends in this video we are going
to see how series RL circuit works by
taking the simple problem so I have
taken a problem based on series RL
circuit so in this problem we are
supposed to calculate the impedance of
the circuit given below in a circuit
what are the things given current
flowing through the circuit is given as
Phi ampere voltage across resistance is
16 volt and voltage across inductor is
12 volt and we are supposed to find out
the impedance of this circuit so in
series RL circuit first I will draw a
voltage triangle so voltage triangle for
series other circuit will be like this
its a V R along the positive x axis
perpendicular to we are taken in
anti-clockwise direction I will have V L
and resultant of V R and V L is nothing
but voltage applied that will make angle
Phi with V R so from this I can say
voltage applied is nothing but root of V
R square plus V L square equal to root
of 16 square plus 12 square if I solve I
will get voltage applied for the circuit
as 20 volt but this is just a magnitude
we need to calculate angle Phi also so
from this I can say tan inverse of V L
upon VR  equal to 5
so 5 I will get as tan universe off
12/16 which is nothing but 36.87
degree now I can say
voltage applied to this circuit is
20 at an angle 36.87
degree volt its  a series
RL circuit so voltage leads current by
angle Phi therefore I consider current
angle as 0 or reference quantity
hence voltage applied is 20 at an
angle 36.87 
42
00:03:02,060 --> 00:03:08,840
degree now getting impedance is very
easy so impedance Z of a circuit is
voltage applied divided by current
flowing through the circuit so it is
equal to 20  at an angle 36.87
degree divided by
current given is 5 ampere  5 at an
angle 0 as I said earlier and
considering this as a reference phasor
so angle is 0  degree so impedance I
am getting as 4  at an angle 36.87
degree ohm  I can
get a separate values of R and XL by
converting this into a rectangle form so
in rectangle form z equal to 3.2
57
00:03:54,919 --> 00:04:10,359 plus J 2 point 4 ohm I need to
compare this value of Z with r plus J
Excel so that I will get resistance of
the circuit as 3.2 ohm  and
inductive reactance XL
as 2.40 ohm  if i know the frequency of
supply I can get L but right now they
have not mentioned anything about the
frequency so lets  keep our answer up
to this only thank you
