Voltage, Current and Power explained

Hey friends, welcome to the youtube channel
ALL ABOUT ELECTRONICS. Today we will see the concept of current,
voltage and power in the electrical circuits. And we will see that how they are related
to each other. So, let's start with the current.

So what is current? So, in simple terms, it can be defined as
a flow of electrical charge. So, to understand the current, first of let's
see the concept of electrical charge. So if you see any atom which is the fundamental
building block of any material, it consists of three primary elements. It contains proton and neutron which resides
in the nucleus and the electron moves around the nucleus in the orbits.

Now, the electron which is moving in the outermost
orbit can be easily knocked out of the atom by applying a little bit of energy. And these electrons which are in the outermost
orbit contributes in the flow of current. So, these electrons possess a negative charge,
while proton possesses a positive charge. Neutrons have a no charge or electrically
they are neutral.

So the same polarity charges have a tendency
to move away from each other. While the opposite polarity charges have a
tendency to move towards each other. The unit of the charge is Coulomb. And it is denoted by symbol Q or q.

When we talk about the charge of electrons
sometimes it is denoted by symbol e. So 1 electron has a charge of 1.6 X 10^ -19
Coulomb. So to have one coulomb of charge, we require
4.28 X 10^18 electrons, which is the inverse of this quantity. So to have one coulomb of charge, we require
the charge of these much electrons.

So as we have understood the concept of charge,
now let's talk about the concept of current. So, let's assume that we have a piece of copper
wire. And electrons are flowing through this copper
wire. And we want to find out that how many electrons
are flowing through this copper wire.

So, let's take one reference point in this
copper wire A-A'. That is the cross section of this copper wire. And let's assume that amount of charge that
is flowing through this copper wire is 1 C. So if 1 coulomb of charge is passing through
this reference point in one second, then we can say that the current which is flowing
through this copper wire is 1 C/S.

Or 1 Ampere. So the current can be defined as a rate at
which this electrical charge is passing through this reference point. The current is defined by a unit of an ampere. And it is denoted by the symbol I.

So to understand the concept of current, let's
take an example of tap water. The amount of water flowing through te tap
depends on the rate at which water particles are coming out of this tap. The higher the rate at which particles are
coming out of the tap. More will be the water flow.

Likewise, the higher the rate at which this
electrical charge or electrons passing through this reference point, the higher will be the
flow of current. So if 5 C of charge is passing through this
reference point in one second, then we can say that the flow of current is five ampere. So to have the movement of this charge, we
require some sort of energy. So, these electrons or electrical charge will
not contribute to the flow of current unless we apply some form of energy or external force.

At room temperature, these electrons move
randomly in all direction. Because of that net motion of flow is zero. So, to get the net motion of flow, we need
to apply some form of energy. So, let's apply this energy in the form of
an external battery, which connected to this copper wire.

So because of this battery, the electrons
will be supplied to the one end of the copper wire. So, electrons which are free electrons in
this copper wire will get repelled with this negative charge which supplied by this battery. And these free electrons will move to the
other end of the copper wire. And at the other end of the copper wire, they
will get attracted to the positive terminal of the battery.

So in this way, we get a flow of electrons
from the negative to the positive direction. So the electrons in the circuit flow from
the negative to the positive terminal. But in the electrical circuits, if you see,
we generally take a flow of current from positive to the negative direction. So that is the conventinal flow of current.

So, the conventional current flows from the
positive to the negative terminal of the circuit. So as we have discussed, to get movement of
this charge we require some sort of energy. And that energy is measured in the units of
a joule. So, let's assume that we have one coulomb
of charge and to move this charge from negative to the positive terminal, we require energy.

That is one joule. So if 1 Joule of energy is required to move
1 Cof charge from negative to the positive terminal then we can say that the potential
difference between the positive and the negative terminal is 1 volt. So, that is a definition of voltage. So, the voltage can be defined as an energy
required or work done to move a unit charge from one point to the another.

So, let's say we have two points A and B.
And at point A, we have 2 C of charge. So to move a 2 C of charge from one point
A to the B, let's say we require a 2 Jouls of energy. So, voltage or potential difference between
this point A and B can be defined as 2 J/2C, that is 1 Volt. The unit of this potential difference or voltage
is VOLT.

And it is denoted by symbol V. So the higher the amount of energy required
to move a charge from one point o the another point, the higher will be the potential difference. So, let's say if 5 C of charge is at point
A and to move this charge from point A to the point B, let's say we require 50 J of
energy. So the potential difference between the points
will be 50 J/5C = 10 Volt.

So to understand this concept, let's take
one example. Let's say we have one ball on the ground. And it's weight is 100 grams. Now, we want to through this ball from the
ground to the top of this building, which is having a height of 10 meters.

So for this task, we require some energy. Let's say for this task we require energy
E1. Now in another case, we have a ball with the
same weight or mass that is 100 gram. And we want to through this ball to the top
of one building which is having a height of 20 meters.

So for that let's say we require energy E2. Now, here energy E2 will be definitely greater
than the E1. Because the height in the second case is more. So the amount of energy required in the second
case will be the more.

So, we can compare this example with the voltage. The higher the difference between the two
points or higher the height of the building, higher the amount of energy is required to
throw a ball. Likewise, the higher the potential difference
between the twp points, more amount of energy is required to move a charge from one point
to the another point. So, now let's see the concept of power in
the electrical circuits.

So the power can be defined as the rate at
which energy is supplied or consumed in the system. So this power is denoted by symbol P.
And mathematically, it can be written as E/t. That is the rate at which energy supplied
or consumed in the system. So it is defined by unit Joule / Second.

Or Watt. While in the earlier case, Voltage mathematically
can be written as V= E/Q. That is the energy required to move a unit
charge. And the current I can be defined as rate at
which electrical charge is moving from the reference point,
that is Q/t.

Now as we were talking about the power, P=
E/t. So, let's understand the concept of power
by taking one simple example. Let's say we have one coulomb of charge at
point A. We want to move this charge from point A to
the point B.

And the energy required for this task is let's
say 5 Joules. And the time required for this task is let's
say 5 seconds. So by the definition of the power, P that
is defined by the rate at which energy is consumed. That is E/t.

Now here, in this case, to move 1 coulomb
of charge, we require 5 Jouls of energy. That is 5 Joules of energy per 1 Colomb. And the time required to move this 1 Coulomb
of charge is 5 seconds, That is 5 seconds / 1 Coulomb. So the power required for this task is 5J
/ 5 seconds, that is 1 watt.

Now, let's generalize this term. Let's say we require E joules of energy to
move Q amount of charge. And the time required for this task is t. That is t seconds for Q coulomb of charge.

That is power. So we can rewrite the term like, (E/Q) * (Q/t)
So E/Q is nothing but Voltage, as voltage can be defined as the energy required to move
a unit charge. And I, that is current can be defined as the
rate at which the charge is moving. So, we can write power as a product of V*I.

So, power can be defined as a product of V*I. So this very useful relationship between the
voltage, power and the current. Now in electrical circuits, The power is either
consumed or it is been supplied. So in electrical circuits, if you see any
element is either dissipating power or supplying a power.

So, how to know that element is supplying
a power or dissipating a power. This can find out by the simple sign convention,
So we will use this sign convention, to know
whether this element is supplying energy or it is dissipating energy. So let's say we have one element,
And the voltage between the two terminal is V. So if the current is flowing out of the positive
terminal of that element then we can say that that element is supplying a power.

Or if the current is flowing into the positive
terminal of that element then we can say that that element is dissipating a power. So, let's take one example to understand it
very clearly. Let's say we have two voltage sources,
which are connected through one resistor. We have one voltage source of 5V,
and another voltage source of 3 V.

They are connected by one resistor R.
So, the current will flow from higher potential to the lower potential, like water flows from
the higher elevation to the lower elevation. So, we will have a current in a clockwise
direction. And because of the flow of current, there
will be a potential drop across this resistorR. Let's say that is Vr.

Now, lets apply a sign convention across all
elements. So across the 5 volt source, the current is
flowing out of the terminal that means, this element or this source is supplying a power. Now, let's see a resistor,
So the current is entering into the positive terminal of the resistor. So the power is dissipated across this resistor.

Now, let's see across this 3 V voltage source. So across 3 V, current is entering into the
positive terminal. So this 3 V source is also dissipating an
energy or power. So 5V is supplying energy and the resistor
and 3V voltage source is dissipating the energy or power.

So by using this sign convention method, in
any network, we can find which elements are supplying the power and which elements are
dissipating the power. So let's summarize what we have seen in this
video. We have seen the current, voltage and power
in the electrical circuits and how they are related to each other. They are related to each other by this
P= V*I relationship.

So, hope you understood what is current, voltage
and power in the electrical circuits. If you have any query or doubts please let
me know in the coment section below. If you like this video, subcribe to the channel
ALL ABOUT ELECTRONICS..

Labels: CURRENT

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