Hey friends, welcome to the YouTube
channel All About Electronics and today
we will see Ohm's law in the electrical
circuit. So Ohm's law is very simple
algebraic relationship between the
voltage, current and the resistor in the
circuit. So, let us say we have one
voltage source which is connected to a
one resistor R.So, because of that the
current will flow through this resistor
R. So, according to the Ohm's law at
constant temperature the electrical
current flowing through a fixed linear
resistor is directly proportional to the
voltage applied across it and it is
inversely proportional to the resistance.
So, the current which is flowing through
this resistor R is directly proportional
to the voltage applied across it and it
is inversely proportional to the
resistance of this resistor. So, now let's
understand this Ohm's law by taking a
water tank analogy. So, let's say we have
one water tank and at the bottom of the
tank we have connected one hose pipe. So
in this analogy the water in the water
tank can be represented as a charge in
the electrical circuits. While the level
of the water in the tank or a water
pressure represents the voltage in the
electrical circuit. The diameter of this
hose pipe represents the resistance
in the circuit and the flow of water
through this hose pipe represents the
current in the electrical circuit. So, now
let's take up one example. Here, we have a
two water tanks which contains an equal
amount of water in the both the tanks.
But the both the tanks have a different
diameter of hose pipe. So, definitely the
tank which has a larger diameter hose
pipe will have a more flow of water. In
the second case,
where the diameter of the hose pipe is
small, the flow of water will be less.
Because the water will observe more
amount of resistance through this lower
diameter hose pipe. While when it flows
through a larger diameter hose pipe, it
feels less amount of resistance. So let's
correlate it with the electrical circuit.
Let us say that we have a two electrical
circuit which has a same voltage sources
but the value of resistance in the both
the circuit is different. In one case one
case it is R1 and in second because it is
R2. And So according to the Ohm's law,
the current flowing in the first circuit
can be given as V devide by R1. In the  second
circuit, it can be given as I 2 is equal to
V devide by R2. Now here, the resistance R2
is less than R 1, so the more current
will flow through this second circuit as
the value of resistance is less. But in
the first circuit, as the value of
resistance R1 is more, So less amount of
current will flow. So for both the
circuits I 2 will be greater than I1.
Now let us take second example in
which we have a two water tanks with the
same diameter of hose pipe but in the
both the tanks the amount of water level
is different. In the first tank we have a
less amount of water, so because of that
pressure exerted at the bottom of this
hose pipe will be less. So because of the
less pressure, the flow of water will be
less.while in the second case, as it
contains more amount of water the
pressure exerted at the bottom of the
hose pipe will be more. Because of the
more pressure the flow of water will be
more through this pipe. So now let us
correlate it with the electrical circuit.
So, let us say we have our two electrical
circuits with a different voltage
sources. But both the circuit contains a
same amount of resistance, that is R.
So, the current flowing through the First
Circuit I1 can be given as V 1 devide
by R. While in the Second Circuit, it can
be even by I2 is equal to V2 /R.
Now here the voltage source V 2 is
greater than V 1, so the more amount of
current will flow through the second
circuit. So we can say that for both the
circuits if V2 is greater than V 1 then
I 2 will be greater than I1. So
through this both both the examples, we
have seen that if we keep one parameter
constant. Let's say if we keep voltage
constant and we change the value of
resistance, or if we increase the value
of resistor R then the current will
reduce in the circuit, or if we keep the
resistance R constant and if we
increase or decrease the value of
voltage in the circuit and accordingly
the current will increase or decrease
proportionally. So, now let's take a
examples based on the Ohm's law.
In the
first circuit we have a one voltage
source with a 5 volt which is connected
to a 10 ohm resistor. So we need to find
what is the current that is flowing
through this 10 ohm resistor. So the
current I can be given as V divide by R. so here the voltage is 5 volt and
the resistance is a 10 ohm. So the
current flowing through this circuit can
be given as a 0.5 ampere, now in the
second circuit if you see we have one 5
volt voltage source which is connected
to a unknown resistor R. And the
current that is flowing through this
circuit is given as a 2 ampere. So we
need to find , what is the value of
this resistance R. So we know that
according to the Ohm's law, I is equal to
V divide by R.So we can write R is equal
to V divide by R. Now here we know the
voltage that is a 5 volt,and the current
that is flowing through that circuit is
a 2 ampere. From this the value of
unknown the resistance will be the 2.5
ohm. so basically this Ohm's law is a
relationship between the voltage, current
and resistor. so if you know any of the
two quantities you can find the third
one.So let's say you know the current
and the resistance in the circuit then
voltage can be defined as V is equal to
I*R. Or if we know the voltage and
current in the circuit then the resistance
R can be given as V divide by I that is V
divide by i .Likewise, current I can be given
as V divide by R. so in the Ohm's law if we
know any of the two quantities we can
find the third one. now so in the last
video we had seen, what is power in the
electrical circuits. And it is given by
relationship P is equal to V *I .so
according to the Ohm's law we know that
the current I can be given as V divide by R
Now let's put this into this equation so
we'll get V*(V/R),that is a
V^2/R. so power can also be
defined by V^2/R. now we know
that what voltage can also be written as
I *R, according to the Ohm's law.So
this power P that is V into I can also
be written as(I*R)*I, that is a
I^2*R. so power can be
defined as either product of voltage
into current
or V^2/R or I^2*R. so
in this way we get a relationship
between the power, voltage, current and
the resistance in the circuit. So let's
see this pie chart which shows all
the possible relationship between the
voltage, current, power and resistor. So
here if we know any of the two
parameters in the circuit let's say if
we know current and power in the circuit
then we can find the remaining two
parameters in the circuit . so if you know
current and power when the voltage can
be defined as a P divide by I. Likewise, the
resistance R can be defined as a P
divide by I square. so in this way if we
know any of the two parameters, we can
find the remaining two . so let's say if
we know power and resistor in the
circuit then we can find the current by
square root P divide by R and the voltage
that is given by square root P into R.
so in this way if you know any of the
two quantities we can find the other two.
so let's take a example based on this
relationship. We have one 10 volt voltage
source which is connected to a unknown
resistor R .And  the current is given that
that which is flowing through the
circuit is a 2 ampere . So, we need to find
the value of this resistor and the power
dissipated across this resistor. so first
of all, let's find the value of this
resistance. so according to the Ohm's law
R is given by V /I .so here voltage is
given that is 10 V and the current
that is flowing to the circuit is a 2 A.
so from that we find that the value of
resistance R is a 5 ohm. Now the power P
we had seen that it can be defined
as V*I. So, here we know the voltage
is a 10 volt and the current is a 2
ampere. The power that is dissipated
across the resistor will be 20 W. Now
let us take one more example, here we
have a unknown voltage source V which is
connected to a 10 ohm resistor. And the
current flowing through the circuit is
given, I is equal to 1 A . So, we need to
find the voltage, this unknown voltage
and the power dissipated across this 10
ohm resistor. So, first of all, let's find
the voltage V which is given by I * R.
So, here we know the I is 1 ampere and
the value of resistor R is a 10 ohm. So
the voltage in the circuit will be the
10 volt. And the unknown voltage source has a
voltage of 10 volt. Now the power P can
be given by I^2*R, that we
already have seen. So here current is 1
ampere that is a 1 square into, R that
is a 10 ohm so we get a 10 W. So, the
power dissipated across the resistor
will be 10 W. So, using this Ohm's
law we can find the voltage, power
current and resistor in an electrical
circuit, if we know any of the two
parameters in the electrical circuit. So
I hope you understood what is Ohm's
Law in the electrical circuit and using
this how you can find the four
different parameters in the electrical
circuit. If you like this video please
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