RMS Current Video Lecture - NEET

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currents part six is brought to you by
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please make sure that you have watched
all the videos to part five before going
ahead with part 6 how discussed about
RMS voltage it is now time to discuss
about RMS current so what does RMS
current so easy to understand now
because now you are all ready for me
familiar to RMS voltage RMS current is
nothing but root mean square current
there also the same thing like for an
alternating current you need to mention
the effective current right so the
effective value of alternating current
is nothing but root mean squared current
so I said it is the effective current
square root of the mean of the squared
function of instantaneous values
supplies the same power to the load as
an equivalent DC circuit so everything
stands the seen right so when we talk
about RMS current it is again
represented as I RMS and this I RMS is
square root of the mean of squared
function of instantaneous values so if
these are your instantaneous values then
this would be your RMS value of current
right so this is in case of a discrete
function similarly if we talk about a
continuous function for example if you
talk about the sine function or our
alternating current which we normally
represent as instantaneous alternating
current is represented as I is equal to
I M sine Omega T so in this case I RMS
is equal to I M divided by root 2 so
everything is similar between RMS
current and RMS voltage right ok so now
we will quickly have an overview of all
the different types of currents which
studied so far we talked about RMS
current we talked about instantaneous
current we talked about average current
we talked about peak value of current so
water I mean let me clarify once and
let's see quickly water I mean so that
you do not get confused with any of this
because what happens is as we go later
we can we see that the current is this
much right so it is up to you to decide
that which value of current is talking
about whether it is RMS current or it
will speak value of current so what are
there different current values which we
talked about one is instantaneous value
the other one is peak value of current
the other one is average value of
current over a cycle and the last one is
the RMS value of current so these things
are not only for current they are also
for voltages or voltages also you have
instantaneous value peak value average
and RMS so when I talk about an
instantaneous value of current so it is
just a quick review so instantaneous
value is I is equal to I M sine Omega T
so here this I is the instantaneous
value this is how we represent current
so what does this I represent it
represents the value of I at every
instant of time so as this Omega T keeps
changing the value of I keeps changing
that means with every instant the value
of current is changing so this is your
instantaneous current this value i M
represents the maximum value which I can
take for example if this is this is how
we represent the instantaneous current
that means the value of I at every point
on this plot is changing right and the
maximum value which this plot can take
is nothing but I M that is the peak
value right so so we got instantaneous
value
and peak value what about rms value
which we talked about just now so rms
value is nothing but peak value divided
by root 2 so it would come somewhere
around this place i rms right so
somewhere below this peak value of
current so this i rms represents nothing
but at the effective value of current
for this coordinating current so it is
the effective value of this alternating
current if somebody sees effectively how
much is this alternating current so you
can see that the effective that overall
the current is this much so that this
much is nothing but your RMS current so
then what is average current so average
current would mean the value of the
current over one complete cycle on an
average or the mean value of current
over one complete cycle so let us so
what is the mean value of current over
one complete cycle I mentioned before
also that this value comes out to be 0
because here your current is positive
here it is negative so they both will
cancel out and it will turn out to be 0
over one complete cycle so do you want
to see how it comes out to be 0 let us
try to calculate I average so this I a
bridge would be nothing but integration
of the entire function over this whole
time that means integration of the
instantaneous current that means let us
suppose the instantaneous current is for
any one instant here right so I want to
integrate it throughout this that is I
want to integrate it over the time
interval or the time period capital T so
I will integrate this from 0 to capital
T since so this would be your sum of
values divided by the number of values
that is how we calculate average right
so this would be divided by T so this
will be equal to 1 by T integration of I
M sine Omega T DT from 0 to capital T so
this comes out to be some integration so
this comes out in this I
we can take outside integration of sine
Omega T is nothing but cos Omega T
divided by Omega from zero to T so this
comes out to be I M divided by T into
Omega and to minus cos Omega T plus cos
0 so this is equal to I M divided by T
Omega so minus cos Omega T and what do
we know Omega is equal to 2 pi by 3 so
we can put that and we get minus cos 2
pi plus 1 because cos 0 is 1 now what is
the value of cos 2 pi cos 2 pi is equal
to 1 so this becomes equal to I M
divided by T Omega minus 1 plus 1 so
this comes out to be 0 therefore the
average value of current over one
complete cycle is equal to 0 so I am
sure now that by looking at an
alternating current if somebody asks you
how much is the alternating current you
can see that the alternating current
doesn't have the same magnitude
throughout it doesn't have a constant
magnitude it keeps changing therefore
there are different values to
characterize or to determine the
ordinate in current you have
instantaneous value to tell the value at
every instant you have RMS value to tell
that effective value of the alternating
current you have average value to tell
the average current over one complete
cycle and you have your peak value which
tells that the current will oscillate
between these two values for example + i
M + - I M so this is plus I M and this
value will correspond to my
I am right so this means that the
current alternating current will
alternate or it will oscillate between
these two values right so these are the
four different values which determine
alternating currents or alternating
voltages right so I hope that by now you
are getting better idea of what an
alternating current is what are we going
to study in this lesson so I also
introduced all those RMS currents
average currents by discussing about
your resistive circuit thank you please
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