This document is an introduction to basic concepts in electrical engineering, covering key topics such as electric circuits, systems of units, charge and current, voltage, power and energy, and types of circuit elements. It defines essential terms, explains relationships between physical quantities, and categorizes circuit elements into active and passive sources. The text emphasizes the importance of the conservation of charge and energy in electrical systems.

1. Chapter 1:
Basic Concepts
Introduction to Electrical
Engineering
Kazmir Fahrier

2. Introduction to Electrical Engineering Basic Concepts
2
• Introduction
• Systems of Units
• Charge and Current
• Voltage
• Power and Energy
• Circuit Elements
Chapter 1 :: Topics

3. Chapter 1: Basic Concepts
Introduction

4. Introduction to Electrical Engineering Basic Concepts
4
Electric Circuit Definition: An electric circuit is
an interconnection of electrical elements,
enabling the transfer of energy or
communication between components.
Introduction

5. Introduction to Electrical Engineering Basic Concepts
5
Introduction

6. Chapter 1: Basic Concepts
Systems of Units

7. Introduction to Electrical Engineering Basic Concepts
7
Systems of Units
International System of Units (SI): The SI system
provides a universal standard for measurements,
adopted globally by engineers since 1960.

8. Introduction to Electrical Engineering Basic Concepts
8
Systems of Units
SI Prefixes: SI prefixes,
based on powers of 10,
make it easy to scale
measurements up or
down (e.g., 600,000,000
mm = 600 km)

9. Chapter 1: Basic Concepts
Charge and Current

10. Introduction to Electrical Engineering Basic Concepts
10
Charge and Current
• Electric Charge: The most basic quantity in electric
circuits, electric charge is an intrinsic property of
atomic particles, measured in coulombs (C).
• Conservation of Charge: Charge cannot be created
or destroyed, only transferred, ensuring that the total
charge in a system remains constant.
• Electric Current: Defined as the rate of change of
charge over time, electric current is measured in
amperes (A) and represents the flow of positive
charges.

11. Introduction to Electrical Engineering Basic Concepts
11
Charge and Current
Mathematically, the relationship between current i,
charge q, and time t is
where current is measured in amperes (A), and
1 ampere = 1 coulomb/second

12. Introduction to Electrical Engineering Basic Concepts
12
Charge and Current
The charge transferred between time to and t is obtained
by integrating both sides of Eq.1
Current need not be a constant-valued function.

13. Introduction to Electrical Engineering Basic Concepts
13
Charge and Current
A direct current (DC) is a current that remains constant
with time.

14. Introduction to Electrical Engineering Basic Concepts
14
Charge and Current
An alternating current (AC) is a current that varies
sinusoidally with time.

15. Introduction to Electrical Engineering Basic Concepts
15
Charge and Current
The direction of current flow is conventionally taken as
the direction of positive charge movement.

16. Introduction to Electrical Engineering Basic Concepts
16
Charge and Current

17. Introduction to Electrical Engineering Basic Concepts
17
Charge and Current

18. Introduction to Electrical Engineering Basic Concepts
18
Charge and Current

19. Chapter 1: Basic Concepts
Voltage

20. Introduction to Electrical Engineering Basic Concepts
20
Voltage
 Voltage (or potential difference) is the energy required
to move a unit charge through an element, measured
in volts (V).
 The voltage between two points a and b in an electric
circuit is the energy (or work) needed to move a unit
charge from a to b.

21. Introduction to Electrical Engineering Basic Concepts
21
Voltage
Mathematically,
where w is energy in joules (J) and q is charge in coulombs
(C).
1 volt = 1 joule/coulomb = 1 newton-meter/coulomb

22. Introduction to Electrical Engineering Basic Concepts
22
Voltage
The plus and minus signs are used to define reference
direction or voltage polarity.

23. Introduction to Electrical Engineering Basic Concepts
23
Voltage
The Vab can be
interpreted in two ways:
(1) Point a is at a potential
of Vab volts higher than
point b.
(2) The potential at point a
with respect to point b is Vab.

24. Introduction to Electrical Engineering Basic Concepts
24
Voltage
It follows logically that in general
• The common term signal is used for an electric
quantity such as a current or a voltage when it is used
for conveying information.
• Like electric current, a constant voltage is called a DC
voltage and is represented by V, whereas a sinusoidally
time-varying voltage is called an AC voltage and is
represented by v.

25. Chapter 1: Basic Concepts
Power and Energy

26. Introduction to Electrical Engineering Basic Concepts
26
• Power is the time rate of expending or
absorbing energy, measured in watts(W).
• We write this relationship as
where p is power in watts (W), w is energy in
joules (J), and t is time in seconds (s).
Power and Energy

27. Introduction to Electrical Engineering Basic Concepts
27
• From Eqs. (1.1), (1.3), and (1.5), it follows that
Power and Energy

28. Introduction to Electrical Engineering Basic Concepts
28
• The power p in Eq. (1.7) is a time-varying
quantity called the instantaneous power.
• If the power has a (+) sign, power is being
delivered to or absorbed by the element.
• If the power has a (-) sign, power is being
supplied by the element.
Power and Energy

29. Introduction to Electrical Engineering Basic Concepts
29
• Passive sign convention is satisfied when the
current enters through the positive terminal
of an element and p = +vi.
• If the current enters
through the
negative terminal,
p = -vi.
Power and Energy

30. Introduction to Electrical Engineering Basic Concepts
30
• The law of conservation of energy must be
obeyed in any electric circuit.
• For this reason, the algebraic sum of power in
a circuit, at any instant of time, must be zero.
Power and Energy

31. Introduction to Electrical Engineering Basic Concepts
31
• From Eq. (1.6), the energy absorbed or
supplied by an element from time to to time t
is
• Energy is the capacity to do work, measured
in joules (J).
1 Wh = 3,600 J
Power and Energy

32. Introduction to Electrical Engineering Basic Concepts
32
Power and Energy

33. Introduction to Electrical Engineering Basic Concepts
33
Power and Energy

34. Introduction to Electrical Engineering Basic Concepts
34
Power and Energy

35. Chapter 1: Basic Concepts
Circuit Elements

36. Introduction to Electrical Engineering Basic Concepts
36
Circuit Elements
Types of Circuit Elements: Circuit elements are
classified into active and passive elements.
Active elements, like generators and batteries, can
generate energy.
Passive elements, like resistors, capacitors, and
inductors, cannot.

37. Introduction to Electrical Engineering Basic Concepts
37
Circuit Elements
• Independent and Dependent Sources:
• The primary active elements are voltage or current
sources, which can either be independent or
dependent.
• Independent sources provide specified voltage or
current regardless of other circuit elements, while
dependent sources rely on other voltages or
currents in the circuit.

38. Introduction to Electrical Engineering Basic Concepts
38
Circuit Elements
Types of Dependent Sources:
Dependent sources are categorized based on the
control type, resulting in four types:
• Voltage-Controlled Voltage Source (VCVS),
• Current-Controlled Voltage Source (CCVS),
• Voltage-Controlled Current Source (VCCS), and
• Current-Controlled Current Source (CCCS).
These are represented with diamond-shaped
symbols.

39. Introduction to Electrical Engineering Basic Concepts
39
Circuit Elements

40. Introduction to Electrical Engineering Basic Concepts
40
Circuit Elements
A voltage source comes with
polarities in its symbol, while a
current source comes with an
arrow, irrespective of what it
depends on.
An ideal voltage source will produce any current required
to ensure that the terminal voltage is as stated, whereas
an ideal current source will produce the necessary voltage
to ensure the stated current flow.

41. Introduction to Electrical Engineering Basic Concepts
41
Circuit Elements
Thus, an ideal source could in theory supply an infinite
amount of energy.
It should also be noted that not only do sources supply
power to a circuit, but they can also absorb power from a
circuit too.

42. Introduction to Electrical Engineering Basic Concepts
42
Circuit Elements

43. Introduction to Electrical Engineering Basic Concepts
43
Circuit Elements