
Introduction 1

Lecture1.1


DC Circuits 16

Lecture2.1

Lecture2.2

Lecture2.3

Lecture2.4

Lecture2.5

Lecture2.6

Lecture2.7

Lecture2.8

Lecture2.9

Lecture2.10

Lecture2.11

Lecture2.12

Lecture2.13

Lecture2.14

Lecture2.15

Lecture2.16


AC circuit 9

Lecture3.1

Lecture3.2

Lecture3.3

Lecture3.4

Lecture3.5

Lecture3.6

Lecture3.7

Lecture3.8

Lecture3.9


Transformer 6

Lecture4.1

Lecture4.2

Lecture4.3

Lecture4.4

Lecture4.5

Lecture4.6


DC GENERATOR and DC MOTOR 5

Lecture5.1

Lecture5.2

Lecture5.3

Lecture5.4

Lecture5.5


HOW TO PASS 1

Lecture6.1


BEE Viva Questions 1

Lecture7.1

Basic Electrical Engineering Viva Questions
Module 1 : DC CIRCUIT
1. What is a direct current (DC) circuit?
● Direct current is a type of electricity that always moves in the same direction. It's
like a line of people holding hands and walking forward in a straight line,like a
oneway street. They never change direction, just like the electricity in a direct
current circuit never changes direction. This type of electricity is produced by
batteries and used in many electronic devices like cell phones, flashlights, and
some trains.
● The electricity flows out of the negative end of the battery, through the light bulb
or other device, and then back into the positive end of the battery. This flow of
electricity in one direction is called direct current.
2. What is a switch and resistor ?
Switch :
Definition 1 : A switch is a button that turns things on and off, like a light switch in
your room.
Definition 2 : A switch is a control mechanism used to connect and disconnect
electrical circuits.
Resistor :
Definition 1 : A resistor is a part that makes electricity flow slower, like a traffic cop
that makes cars slow down.
Definition 2 : A resistor is an electrical device used to limit the flow of current in an
electrical circuit.
So, switches and resistors are like little helpers in a circuit, making sure everything
works safely and properly.
3. Can you explain Ohm's Law?
● Ohm's law is a scientific rule that tells us how electricity behaves. It says that the
amount of electricity flowing through a material (like a wire) is related to the
voltage (or pressure) of the electricity and the resistance of the material.
● Let's say you have a light bulb. The light bulb needs electricity to work, and it gets
electricity from the wires connected to it. The amount of electricity that flows
through the wires and into the light bulb is like the water flowing through a pipe.
● Now, let's say you want to make the light brighter. You can do this by either
increasing the water pressure in the pipe (which is like increasing the voltage in the
wires), or by making the pipe narrower (which is like reducing the resistance in the
wires).
● If you increase the voltage, more electricity will flow into the light bulb, and the
light will get brighter. But if you reduce the resistance, more electricity will flow,
and the light will also get brighter.
● So, just like with the pipe and the water, the amount of electricity flowing into the
light bulb (measured in amps) is related to the voltage (measured in volts) and the
resistance (measured in ohms) of the wires. And this relationship is what we call
Ohm's law.
4. How does Ohm's law is applied in DC circuits?
● Ohm's law is like a recipe for electricity in a DC circuit. It tells you how
much electricity will flow in the circuit if you know two things: the voltage
(like the pressure) and the resistance (like the size of the pipe).
● Imagine you have a battery, wires, and a light bulb. The battery is like a
pump that pushes the electricity through the wires. The wires are like pipes,
and the light bulb is like a faucet that lets the electricity out. The light bulb
also gets hot and uses up some of the electricity, just like a water tap uses
up some of the water.
● Now, if you want the light to shine brighter, you can either increase the
voltage from the battery or decrease the resistance in the wires. But if you
increase the voltage too much, or decrease the resistance too much, the
light bulb could burn out. So you have to be careful and use Ohm's law to
find the right balance.
● So, in a DC circuit, Ohm's law helps you understand how the different parts
of the circuit are connected and how they work together.
5. What are capacitors and inductors in a DC circuit?
● A capacitor is like a bucket for electricity. When you pour water into a bucket, it
fills up and holds the water until you need it. A capacitor does the same thing with
electricity  it stores it and releases it when needed.
● An inductor is a device that stores electrical energy in a magnetic field. It looks
like a coil of wire and when you pass electricity through it, a magnetic field is
created and stores the electric energy. It's kind of like an invisible battery that
stores electricity and can be used later.
6. What is Kirchhoff’s law?
Kirchhoff's laws are like rules for understanding how electricity flows in a circuit.
They help us predict and control the flow of electricity in a circuit.
There are two laws of Kirchhoff:
The first law, known as Kirchhoff's Current Law ( KCL )
● KCL states that the “total current entering a junction or node is exactly equal to the
current leaving the node.” It's like a river where the water flowing inside a tunnel
must equal the water coming out from that tunnel. The same goes for electricity.
● In other words, the algebraic sum of all the currents entering the node must be
equal to the algebraic sum of all the currents leaving a node.
In the first Diagram you can see there are six currents i_{1} , i_{2} , i_{3} , i_{4} , i_{5 ,} i_{6}
respectively. Where i_{1} , i_{2} , i_{3} are incoming currents whereas i_{4} , i_{5} , i_{6} are the
currents going out. The center point (node) is called a junction.
● Junction is a point where two or more currents meet. For example, as we all know
that a railway station where express trains from various cities come is known as a
junction because that is the place where every train comes and stops or meets.
Similarly in terms of electricity the point at which two or more electric currents
meet is said to be a junction.
The second law is known as Kirchhoff's Voltage Law ( KVL )
Kirchhoff’s voltage law states that the voltage around a loop equals the sum of every
voltage drop in the same loop for any closed network and equals zero.
7. Discuss the concept of electrical potential difference ( Voltage ) .
● Electrical potential difference is like a water pump. Imagine you have a
pool of water at the bottom of a hill, and you want to pump the water to the
top of the hill. The water pump will push the water up the hill and create a
difference in height between the water at the bottom and the water at the
top. This difference in height is like the electrical potential difference.
● In electricity, we have something called voltage, which is the same thing as
electrical potential difference. Voltage is the difference in electrical energy
between two points in a circuit, just like the difference in height between
the bottom and top of the hill with the water pump. When you have a high
voltage, it means that there is a lot of electrical energy, and it can push
electrical charges (like electrons) around a circuit.
The above diagram clearly explains the concept of electric potential difference. i.e
Voltage
8. How does electrical potential difference (Voltage) relate to the flow of current in a
circuit?
● Assume a river with water flowing from one end to the other. The water is
like electricity, and the speed of the water flow is like the flow of electric
current.
● Now, imagine there is a dam in the middle of the river. The water behind
the dam is like the electrical energy stored in a battery. The dam is like a
voltage source, and it pushes the water down the river. The higher the dam,
the stronger the push and the faster the water will flow.
● In the same way, voltage pushes the electrons in a circuit, and the higher
the voltage, the faster the electrons will flow, which is what we call electric
current. So, you can think of voltage as the "push" that makes the electrons
flow in a circuit, and current as the flow of electrons that powers the
devices in the circuit.
9. Explain Thevenin's theorem
● The Thevenin's Theorem states that any linear network with voltage
sources, current sources, and resistors connected together can be reduced to
an equivalent circuit with just a single voltage source and a single resistor.
This equivalent circuit is known as a Thevenin equivalent circuit.
Let's simplify it even more with an example.
● Imagine you have a bunch of batteries and light bulbs connected together
to make a circuit. Thevenin's theorem says that we can think of the whole
circuit as just one battery and one light bulb, which represents the whole
circuit in a simple way. This makes it easier for us to understand and work
with the circuit.
● Think of it like cooking a big feast for many people. You can cook each
dish separately and then combine them together, or you can mix everything
together and cook the whole thing at once. Thevenin's theorem is like the
second option, where we simplify the whole thing so it's easier to
understand and work with.
● By this we get to know that Thevenin's theorem is a way to simplify a
complex electrical circuit so it's easier to understand and work with.
10. What is Norton's theorem?
● It states that any linear electrical network containing only voltage sources,
current sources, and resistors can be replaced by a single current source in
parallel with a single resistor. The value of the resistor is equal to the sum
of the resistances in the original network, and the value of the current
source is equal to the sum of the currents in the original network.
This theorem is useful in circuit analysis because it can be used to reduce a complex
circuit into a simple equivalent circuit.
Let's Make it More Simple :
● Think of an electrical circuit as a garden pipe. Just like water flows through
a pipe, electricity flows through a circuit. But sometimes, the pipe might
have lots of twists and turns, which makes it harder for the water to flow.
● Norton's theorem says that even if a circuit is really complicated, it can be
replaced by a simple circuit that acts just like it. This simple circuit is like a
single pipe that's easy to understand. Instead of water, this pipe has
electricity flowing through it, and we can measure how much electricity is
flowing just like we can measure how much water is flowing in the original
pipe.
● So, Norton's theorem helps us understand complicated circuits by making
them simple, which makes it easier for us to study how electricity flows
and how we can control it.
11. Discuss some common applications of DC circuits in batteries and rectifiers?
Direct Current (DC) circuits are widely used in many applications involving
batteries and rectifiers. Here are a few common applications of DC circuits in these
areas:
● Batteries: DC circuits are used in many types of batteries, such as
leadacid batteries, nickelcadmium (NiCad) batteries, and lithiumion
batteries. These batteries store electrical energy and can supply it to
devices that need it, such as flashlights, cell phones, laptops, and electric
vehicles.
●
Rectifiers: Rectifiers are devices that convert Alternating Current (AC) to
Direct Current (DC). They are used in many applications, such as power
supplies for electronic devices, charging batteries, and welding. One
common application of rectifiers is in power supplies for electronic
devices, where the AC power from the wall socket is converted to DC to
power the device.
o Rectifiers are like magic boxes that change one type of electricity
into another. Some things, like cell phones and computers, need a
special type of electricity called DC to work. Rectifiers take regular
electricity (AC) and change it into DC, so these things can use it.
●
Solar Cells: Solar cells are devices that convert sunlight into electrical
energy. They are connected in series to form a solar panel, which is then
used to charge batteries or to provide power to devices directly. Solar cells
use DC circuits to store and use the electrical energy they produce.
●
Electric Motors: DC motors are widely used in many applications, such as
electric vehicles, toys, and industrial applications. The DC voltage from a
battery or a rectifier is used to control the speed and direction of the motor.
These are just a few examples of the many applications of DC circuits in
batteries and rectifiers.
12. Maximum Power Transfer Theorem.
● The Maximum Power Transfer Theorem is a principle in electrical engineering that
states that to transfer the maximum amount of power from a power source (such as
a battery or generator) to a load (such as a resistor or motor), the load resistance
should be equal to the internal resistance / Thevenin's equivalent Resistance of the
source.
● The Maximum Power Transfer Theorem is a useful tool for electrical engineers in
the design and analysis of electrical circuits. By understanding the theorem and
applying it in the design process, engineers can optimize the performance of
electrical systems and ensure that the maximum amount of power is delivered to
the load.
Let us go with an example,
● Imagine you have a water pipe and you're trying to fill a bucket with water as fast
as you can. If the hole in the bottom of the bucket is too small, the water will take a
long time to fill the bucket. But if the hole is too big, the water will splash out and
you won't be able to fill the bucket.
● The same thing is true for electricity. If the electrical circuit that you're trying to
power has too much resistance, not enough electricity will flow through to do what
you want. And if the circuit has too little resistance, some of the electricity will be
wasted and not used to power the circuit.
● The Maximum Power Transfer Theorem says that the best way to make sure the
most electricity gets to where you want it to go is to have the right amount of
resistance in the circuit. If the resistance of the circuit is just right, the most
electricity will flow through and the circuit will work at its best.
● So, this theorem helps us make sure that the electricity we're using is not wasted
and that we're getting the most power to where we want it to go.