Hello friends in this video we are going
to see a simple problem based on
parallel resonance the statement of
problem is like this a coil of
inductance 31.8 millihenry with
resistance of 12 ohm is connected in
parallel with a capacitor across 250
volts 50 Hertz supply determine the
value of capacitance if no reactive
current is taken from the supply so lets
 solve before solving lets draw a
circuit diagram so here what they are
given a coil so coil is nothing but the
resistance in series with inductance the
resistance is 12 ohm inductance is 31.8
 milli Henry so this coil is
connected in parallel with a capacitor
whose value we are supposed to find out
whole circuitry is connected across 
250 volt 50 Hertz supply we have to
obtain the value of C such a way that no
reactive current is taken from the
supply so this statement is very very
important why because this is telling
you this is a parallel resonance circuit
so I will write no reactive current is
taken from the supply implies resonance
condition or I should say parallel
resonance because parallel circuit is
given once you have determined it is a
resonance rest of the problem will be
very easy because you have to just apply
one formula so resultant frequency F R
equal to 1 upon 2 pi root of 1 upon L C
minus R square divide
by L square so if you address the value
of capacitor such a way that this will
become resonating frequency so 50 Hertz
equal to 1 upon 2 pi root of 1 upon what
is the value of L its a 31.8
mili henry see we are
supposed to calculate R is 12 ohm so its a 12
square s square is again 31.8 into
10 raise to minus 3 whole square so if
you solve what we will get 50 equal to 1
upon 2 pi root of if you solve this it
will be 1 upon 0.0318c and answer for
this will be 142399.4304
if I further simplify it will be
98696.044
equal to 31.4465
upon C minus 142399.4304
 in this equation only
unknown is C and that is equal to 1.3043
into 10 raise to minus 4
ferhite so it is identify its a
resonance and apply the formula and get
answer thank you
