notes of fundamental dc and ac circuits

1. ECE249: BASIC ELECTRICAL AND ELECTRONICS ENGINEERING
UNIT 1
Fundamental of DC and AC Circuits
Lecture 1 and 2 Prepared by Teacher: Dr. Krishan kumar, Professor, SEEE

2. Course Assessment Model
Marks Break Up:
CA (Two best out of Three) 25
MTE 20
ETE 50
Total 100
CA-1 CA-2 CA-3
Marks 30 (12.5 weightage) 30 (12.5 weightage) 30 (12.5 weightage)
Evaluat
ion
Proced
ure
6 Questions of 5 marks
each: Syllabus: Unit 1
Solve 3 questions on circuit
simulator , also solve on paper,
merge both solutions in one
answer book and upload online
on UMS
One Arduino based group Project (group size:04
student) , students from same class group will create
project groups, Project report and viva-10M,
Innovativeness in the project-10M, Working Model-
10M (Plagiarism: Report should be written by the
group members only/not copied from online sources)
Condu
ct
Assignment of task on
UMS: 6th Lecture,
Conduct of test :9th
Lecture
(after conduct: retest/
appear on another
date /with other
group/health etc. not
allowed)
Assignment of task on UMS:24th
lecture, Submission: 27th Lecture
: (9:00PM),
)Late submissions due to
internet/ums/health will not be
entertained. )
Assignment of task on UMS:14th lecture, Submission:
31st Lecture (tutorial in the same week). Report should
be uploaded on ums by 9:00PM-
Late Report submissions due to issues e.g. internet/
ums/health will not be entertained.
Project title submission: 17th Lecture
Must update progress of Project to the faculty on
weekly basis in tutorial class (1st 5 min), carelessness
will lead to deduction of marks
Test will be conducted
in lecture class
Online uploading on UMS by the
students
Upload report on UMS, and submit hardware project
to faculty
MTE 40 questions of MCQ type based on 1st unit 1- unit 3 (No direct MCQ questions )
ETE 30 questions of MCQ type based on 1st unit 1- unit 6 5 questions, 10 marks each (4 out of 5): Unit-1 to unit

3. WhyECESubjectforCSEStudents?
• Electrical engineers largely deal with
hardware, while computer scientists deal
with software.
• Electrical engineers are the ones that
design circuits, processors, memory, and
establishing wireless communication.
• This subject provides the basic
understanding regarding the hardware
components of the computer.
Hybrid Branches:
• MIT: Department of Electrical Engineering
and Computer Science
• UC Berkeley: Electrical Engineering &
Computer Sciences

4. Electrical and Electronics Engineering
• Computer engineering focuses on the creation and design of computer
software, whereas electrical engineering focuses on the development of
anything powered by electricity.
• Electrical engineering concerns the generation, distribution and
electricity on a large scale, while electronic engineering is about the
components and systems that make electronic devices work.

5. ElectricalvsElectronics
Electrical Electronics
Deals with larger voltage (typically 220 V, India).
Factories and power stations, may require up to
11,000 volts.
Deals with smaller voltage (1.5 V to 12 Volts)
Larger in size Smaller in size
Example: Motor, transformer, generator Example: Diode, Transistor, OP-amp, MOSFET
Digital Electronics

6. Unit I Fundamentals of DC and AC Circuits
Unit I Fundamentals of DC and AC circuits
Resistance, inductance, capacitance, voltage, current, power and energy
concepts, ohm's law, Kirchhoff’s laws, voltage division rule, current division
rule, mesh and nodal analysis, dependent and independent sources,
Thevenin’s theorem, Norton’s theorem, alternating current and voltage,
definitions of amplitude and phase, average and RMS value of an AC signal

7. Topics
• Electrical Circuit
• Voltage and Current
• Power and Energy
• Network Component-Active/Passive
• Resistance, Inductance and capacitance
• Open and Short Circuit
• Series and Parallel connection
• Ohm's law
• Applications and Limitation of Ohm’s Law

8. KEYWORDS
• AC
• DC
• I
• V
• R
• C

9. Electrical Circuit
External video link
https://www.youtube.com/watch?v=VnnpLaKsqGU
Electric circuit, path for transmitting electric current. An electric circuit includes a device that
gives energy to the charged particles constituting the current, such as a battery or a generator;
devices that use current, such as lamps, electric motors, or computers; and the connecting wires or
transmission lines.
direction of current is from the positive end of the voltage
source to the negative end (opposite the direction of flow of
electrons).

10. Charge and Current
• Charge: Charge is an electrical
property of the atomic particles of a
matter.
S.I Unit: Coulomb ( C )
Symbol: Q
•Current: Rate of change of charge.
OR
Continuous flow
S.I Unit: Ampere (A )
Symbol: I
of electrons in an electrical circuit.

11. How current is created?
When a voltage is applied to a conductor or semiconductor, electric current starts
flowing.
In conductors, positively charged protons are held in a fixed position and the
negatively charged electrons move from one place to another place by carrying the
charge. Thus, electrons conduct electric current in conductors.
Current is the flow of an electric charge. It is an important quantity in
electronic circuits. Current flows through a circuit when a voltage is placed across
two points of a conductor.
-----------Flow of Electrons----
In an electronic circuit, the current is the flow of electrons

12. Charge and Current
• Mathematically,
Or, in simple terms:
So, 1 Ampere = 1 coulomb/ 1 second.

13. QUICK QUIZ (Poll 1)
The rate of flow of an electric charge is known as:
A. Electric potential
B. Electric conductance
C. Electric current
D. None of these

14. QUICK QUIZ (Poll 2)
Current flows in a circuit when

15. DC and AC current
There are two kinds of current electricity:
direct current (DC) and alternating current
(AC).
With direct current, electrons move in one
direction. Batteries produce direct current.
In alternating current, electrons flow in both
directions.
.

16. Which is better AC or DC?

17. Answer
Alternating current is cheaper to generate and
has fewer energy losses than direct current
when transmitting electricity over long
distances.

18. Voltage
• Voltage (also known as electric potential difference, electromotive
force emf, electric pressure, or electric tension) is defined as the
electric potential difference per unit charge between two points in
an electric field. Voltage is expressed mathematically (e.g. in
formulas) using the symbol “V” or “E”.
• When a voltage source is connected to a circuit, the voltage will
cause a uniform flow of charge carriers through that circuit called a
current. In a single (one loop) circuit, the amount of current at any
point is the same as the amount of current at any other point.

19. Symbol
• The volt (symbol: V) is the derived unit for
electric potential, electric potential
difference (voltage), and electromotive force.
• It is named after the Italian physicist
Alessandro Volta (1745–1827).

20. Voltage(Water Tank )Example
Current flowing in a circuit is like the
flow of water from a higher
reservoir/TANK/POND to a lower one, as
shown in the animation on the right. The
pump acts to maintain a pressure
difference between the two reservoirs.
This pressure difference allows water to
flow in the pipe that connects the two
reservoirs and do some work in turning
the wheel.
Similar to the pump, a battery maintains a
suitable electrical pressure difference
(potential difference) across the circuit
and allows charge to flow resulting in
electrical current.
When describing voltage, current,
and resistance, a common analogy is
a water tank. In this analogy,
charge is represented by
the water amount, voltage
is represented by the
water pressure, and current
is represented by the
water flow. So for this
analogy, remember:
• Water = Charge
• Pressure= Voltage
• Flow = Current

21. Voltage
• It is the energy (Work) required to
move a unit charge through an
element.
S.I Unit: Volt ( V ) Symbol: V
External video link
https://www.youtube.com/watch?v=z8qfhFXjsrw
Voltage is the pressure from an electrical circuit's
power source that pushes charged electrons
(current) through a conducting loop, enabling them
to do work such as illuminating a light.

22. Difference between Voltage and Current
• The important difference between voltage and current.
Voltage is the potential difference between two points in
an electric field, which causes current to flow in the
circuit.
• Current is the rate of flow of electrons is called current.
Voltage is the cause of current (being an effect).

23. Power and Energy
• Power: Rate at which the work is done.
OR
Time rate of absorbing or supplying energy
S.I Unit: Watts ( W ) Symbol: P
Mathematically,
Implies, 𝑃 = 𝑉. 𝐼
Electrical energy defines the energy generated due to the
movement of charge carriers in a conductor. While electrical power
specifies the rate of consumption of electrical energy by a device.
The SI unit of electrical energy is Joules. But electrical power is
measured in Watts (or KWh).

24. Power and Energy
• Energy: Capacity of doing work.
S.I Unit: Joules(J) Symbol: E

25. QUICK QUIZ
Home Assignment
An electric bulb is rated 220 volt and 100 watt, Power consumed by it when
operated on 110 volt is :
A.70W
B.60 W
C. W
D.25W

26. Example-Electrical Energy
Lightning, example of electrical energy?
batteries are examples of electrical energy
-sources of electrical energy-
The three major categories of energy for electricity generation are fossil fuels (coal,
natural gas, and petroleum), nuclear energy, and renewable energy sources. Most
electricity is generated with steam turbines using fossil fuels, nuclear, biomass,
geothermal, and solar thermal energy.

27. Question
What is the best source of electrical energy?

28. Answer
Hydroelectric power, using the potential energy
of rivers, is by far the best-established means of
electricity generation from renewable sources.
It may also be large-scale – nine of the ten
largest power plants in the world are hydro,
using dams on rivers.

29. Question
Why electrical energy is best source of energy?

30. Answer
• Electrical energy systems. Electrical energy is one of the most
commonly used forms of energy in the world.
• It can be easily converted into any other energy form and can be safely
and efficiently transported over long distances.
As a result, it is used in our daily lives more than any other energy source.

31. Network Components
Active Passive
Battery
Transistor, Op-amp, etc
Resistance (R) Capacitance (C)
Inductance (L)
Active components are the elements or devices which are capable of providing
or delivering energy to the circuit. Passive components are the ones that do not
require any external source for the operation and are capable of storing energy in
the form of voltage or current in the circuit.
Common examples of active components include:
• Voltage sources.
• Current sources.
• Generators (such as alternators and DC generators)
• All different types of transistors (such as bipolar junction transistors,
MOSFETS, FETs, and JFET)
• Diodes (such as Zener diodes, photodiodes, Schottky diodes, and LEDs)

32. Question
What do you mean by passive device?

33. Answer
A device that does not require a source of energy for its operation.
Examples of passive devices are electrical resistors, electrical capacitors, diodes,
optical fibers, cables, wires, glass lenses, and filters.

34. Question
What is the difference between active and passive
circuit elements?

35. Answer
Active components can inject power into a circuit and are
capable of electrically controlling and amplifying the flow
of electrical current,
whereas passive components cannot.
Unlike active components, passive components either
consume or store energy.

36. Resistance
• Resistance: It is an opposition to
the flow of current.
S.I Unit: Ohm (Ω) Symbol: R
A resistor is a passive two-terminal electrical
component that implements electrical resistance
as a circuit element.
In electronic circuits, resistors are used to
reduce current flow, adjust signal levels, to
divide voltages, bias active elements, and
terminate transmission lines, among other uses.

37. Resistor Category
Fixed Resistors and Variable Resistors. A fixed resistor is one for which
the value of its resistance is specified and cannot be varied in general
-Linear resistors are those in which current produced is directly
proportional to the applied voltage. Their current versus applied voltage
is straight and linear. In other words, their resistance remains constant.
-Non-Linear resistors are those whose current does not change linearly
with changes in applied voltage.

38. Example
Carbon Composition Resistors.
Wire wound Resistors.
Thin Film Resistors.
Carbon Film Resistors.
Metal Film Resistors.
Thick Film Resistors.
Metal Oxide Resistors.
Cermet Oxide Resistors (Network Resistors)

39. Appliances such as electric heaters, electric ovens and toasters all use resistors to
turn current into heat, then using the heat lost from this resistor to warm the
surrounding area.
-----Resistors are used for many purposes.
A few examples include limiting electric current, voltage division, heat generation,
matching and loading circuits, gain control, and setting time constants.
They are commercially available with resistance values over a range of more than
nine orders of magnitude.

40. Capacitance
• Capacitance is the ability of a device to store electrical energy in an electrostatic field.
• A capacitor is a device that stores energy in the form of an electrical field..
• A capacitor is made of two conductors separated by a dielectric.
S.I Unit: Farad (F) Symbol: C Two important
Properties:
1.No current flows through the capacitor, if the voltage remains constant.
2.Voltage across a capacitor cannot change instantaneously.

41. • Capacitance is the ability of a device to store electric charge,
So, the electronic component that stores electric charge is
called a capacitor.
• The simplest capacitor consists of two flat conducting plates
separated by a small gap.
• The potential difference, or voltage, between the plates is
proportional to the difference in the amount of the charge on
the plates.
• This is expressed as Q = CV, where Q is charge, V is voltage
and C is capacitance.

42. Question
What is the relation between capacitance and
resistance?

43. Answer
Resistance is the measure of the amount of energy dissipated by the
resistor. While capacitance is basically but the amount of charge stored
by the capacitor. The resistance of the resistor is given by R = V/I.
Whereas, the capacitance of the capacitor is given as C = Q/V.

44. Question
What is difference between capacitor and resistance?

45. Answer
A resistor is an electronic component used to resist the
flow of current in a circuit. It's more like a friction which
restricts energy. A capacitor, on the other hand, is an
electronic component used to store electrical charge.
It generally opposes changes in current in electrical and
electronic circuits.

46. Inductor
• An inductor is an electronic component consisting of a coil of
wire with an electric current running through it, creating a
magnetic field. One henry is the amount of inductance that is
required to induce 1 volt of electromotive force (the electrical
pressure from an energy source) when the current is changing
at 1 ampere per second.
• One important application of inductors in active circuits is
that they tend to block high-frequency signals while letting
lower-frequency oscillations pass.
• This is the opposite function of capacitors. Combining the
two components in a circuit can selectively filter or generate
oscillations of almost any desired frequency.

47. Inductance
Inductance is the characteristics of an electrical conductor
that opposes a change in current flow.
•An inductor is a device that stores energy in a magnetic
field.
•When a current flows through a conductor, magnetic
field builds up around the conductor. This field contains
energy and is the foundation for inductance
S.I Unit: Henry ( H )
Symbol: L Two important Properties:
1. No voltage appears across an inductor, if the current through it
remains constant.
2.The current through an inductor cannot change instantaneously.

48. The larger the self-inductance L of a device, the greater
its opposition to any change in current through it.
For example, a large coil with many turns and an iron
core has a large L and will not allow current to change
quickly.

49. Question
Why is L used for inductance?

50. Answer
The symbol L for inductance was chosen to honor
Heinrich Lenz (1804–1865), whose pioneering
work in electromagnetic induction was
instrumental in the development of the final
theory.
Lenz' gave us the minus sign and we honor him
with the symbol L.

51. Question
What is inductor formula?

52. Answer
VT = V1 + V2 +V3. We know that the voltage across an inductor is given
by the equation. V = L di / dt.

53. Key Difference – Inductance vs Capacitance
• The key difference between inductance and capacitance is that inductance is a
property of a current carrying conductor which generates a magnetic field
around the conductor whereas capacitance is a property of a device to hold and
store electric charges.
• The behavior of the inductor is based on the properties of the magnetic field
generated in a coil of wire. In fact, the inductor is basically a coil of wire.
• The behavior of the capacitor is based on the properties of the electric field
created in a dielectric (non-conductor) placed between two conductors.
• The capacitor is basically a nonconductor sandwiched between two conductors.
Energy can be stored in, but not generated by, an inductor or a capacitor, so
these are passive devices. The inductor stores energy in its magnetic field; the
capacitor stores energy in its electric field.

54. QUICK QUIZ (Poll 5)
Identify the passive element
A. Battery
B. Transformer
C. Transistor
D. OP-amp
E. None of these

55. QUICK QUIZ (Poll 6)

56. Ohm’s Law
Where, Resistance
𝐼
=
• Ohm’s law states that:
“the current in an electric circuit is directly proportional to the voltage across
its terminals, provided that the physical parameters like
temperature, etc. remain constant”
Mathematically,
𝐼 ∝ 𝑉
Or,
𝑉
𝑅

57. Resistivity Table

58. Conductance
• A useful quantity in circuit analysis is the reciprocal of resistance R,
known as conductance and denoted by G
𝐼
• 𝐺 = 𝑅
= 𝑉
• S.I Unit: mho (ohm spelled backwards) or Siemens
• Symbol:

59. Ohms Law Matrix Table
Ohms Law Matrix Table

61. Ohms Law Example No1
For the circuit shown below find the Voltage (V), the Current (I), the
Resistance (R) and the Power (P).
Voltage [ V = I x R ] = 2 x 12Ω = 24V
Current [ I = V ÷ R ] = 24 ÷ 12Ω = 2A
Resistance [ R = V ÷ I ] = 24 ÷ 2 = 12 Ω
Power [ P = V x I ] = 24 x 2 = 48W

62. Short-circuit and Open-circuit
•For a short circuit, R = 0 Ω• For an open circuit, R =Ω
•Therefore, V = I.R = 0 V • Therefore, I = V/R = 0 V
•NOTE: (current, I can be of any value)
• • NOTE: (voltage,V can be of any value)
External video link
https://www.youtube.com/watch?v=D4iYlgCEFhw

63. Applications of Ohm’s Law
1. To find unknown Voltage (V )
2. To Find unknown Resistance (R )
3. To Find unknown Current (I )
4. Can be used to find Unknown Conductance (G)=1/R
5. Can be used to find unknown Power (P)=VI
6. Can be used to find unknown conductivity or Resistivity

64. Applications of Ohm’s Law
1. It is widely used in circuit analysis.
2. It is used in ammeter, multimeter, etc.
3. It is used to design resistors.
4. It is used to get the desired circuit drop in circuit design (Example,
Domestic Fan Regulator).
5. Advanced laws such as Kirchhoff’s Norton’s law, Thevenin’s law are based
on ohm’s law.
6. Electric heaters, kettles and other types of equipment working principle
follow ohm’s law.
7. A laptop and mobile charger using DC power supply in operation and
working principle of DC power supply depend on ohm’s law.

65. Limitations of Ohm’s Law
• Ohm’s law holds true only for a conductor at a constant temperature. Resistivity
changes with temperature.
• Ohm’s law by itself is not sufficient to analyze circuits.
• It is NOT applicable to non linear elements, For example, Diodes, Transistors,
Thyristors, etc.
• This law cannot be applied to unilateral networks.

66. QUICK QUIZ (Poll 7)
The voltage and the conductance of
the given circuit is:
A. 30V, 10 µS
B.30 mV, 100 µS
C. 30V, 100 µS
D. 30mV, 10 µS

67. QUICK QUIZ (Poll 8)
The power of the given circuit is:
A. 60 mW
B. 70 mW
C. 80 mW
D. 90 mW

68. Series Connection
• SERIES CONNECTION: Two or more elements are in series if they
exclusively share a single node and consequently carry the same

69. current.

70. Point to Remember for Series Circuits

71. Parallel Connection
• PARALLEL CONNECTION: Two or more elements are in parallel if
they are connected to the same two nodes and consequently
have the same voltage across them

73. Battery Voltage In Series And Parallel

74. Note: Resistors in series behave as a single resistor whose resistance is equal to the sum of the
resistances of the individual resistors.

75. Resistors in Parallel
.

76. How to find Equivalent Resistance for Series-
Parallel Combinations

77. Example: To find𝑹𝒆𝒒

78. QUICK QUIZ (Poll 9)
Find Equivalent Resistance in Ohms?
A. 5
B. 10
C. 15
D. 20

79. QUICK QUIZ (Poll 10)
Find Equivalent Resistance in Ohms?
A. 12
B. 17
C. 19
D. 29

80. Useful Links
• http://www.dynamicscience.com.au/tester/solutions1/electric/voltag
e.htm
• https://gfycat.com/directhauntinglamb
• https://www.youtube.com/watch?v=NfcgA1axPLo