This document provides an overview of electrical circuits. It defines key concepts like charge, electric field, electromagnetic field, and current. It discusses the different types of circuit elements including active elements like voltage sources and passive elements like resistors, inductors, and capacitors. It describes circuit elements as being uni-directional or bi-directional, linear or non-linear, lumped or distributed, and uni-lateral or bi-lateral. Resistors are introduced as a fundamental passive element that limits current flow and is represented by the letter R.

1. Electrical Circuits
Dr. Radhika Dora

2.  A fundamental form of energy observable in positive and
negative forms that occurs naturally (as in lightning) or is
produced (as in a generator) and that is expressed in terms of
the movement and interaction of electrons
Electricity = The city where electrons live

3. UNIT–I: Introduction to Electrical Circuits:
• What is Charge
• What is Electric Field or Voltage
• What is Electromagnetic Field
• What is Electric Current
• Definition of Circuit and Network:
• Types of Elements of Circuits
• Active Elements
• Passive Elements
• Basic Laws used to Analyse circuits
• Network Reduction Techniques
• Analysis Techniques

4.  Electric charge is a feature of matter that causes a force when placed into an
electromagnetic field. Charge is measured with Coulombs (C).
 Current is the rate of flow of charge
 The electric field is a vector quantity that exists at every point in space. The
electric field at a location indicates the force that would act on a unit positive test
charge if placed at that location.
 Electric field, an electric property associated with each point in space
when charge is present in any form.
 An electric field (sometimes abbreviated as E-field) surrounds an electric charge,
and exerts force on other charges in the field, attracting or repelling them. Electric
fields are created by electric charges, or by time-varying magnetic fields.
 An electromagnetic field (also EM field) is a classical (i.e. non-
quantum) field produced by moving electric charges

5. Types of Network/Circuit Elements:
• Active and Passive Elements
• Uni Directional and Bi Directional Elements
• Linear and Non Linear Elements
• Lumped and Distributed Elements
• Uni Lateral and Bi lateral Elements

6. Active and Passive Elements
• An Active Element supplies energy to an electric circuit, and
hence has the ability to electrically control the flow of charge.
• A Passive Element can only receive energy, which it can either
dissipate or absorb.

7. Examples of Active Elements:
• 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)

8. Examples of PASSIve Elements:
•Resistors
•Inductors
•Capacitors
•Transformers

9. Uni DIRECTIONal and BiDIRECTIONal Elements
• If the element allows the current to flow in both directions then it is
called as a Bidirectional element
Examples for Bidirectional elements are : Resistors, Inductors,
capacitors, etc.
• If the element allows the current to flow in only one direction then it
is called as a Uni directional element
Examples for Unidirectional elements are : Diodes, Transistors, etc

10. Linear and Non Linear Elements
If the relation between Voltage and current is linear then the element is
called Linear element otherwise it is called as Non linear element.
i.e., Linearity Property need to be satisfied by the element.
Linearity = Homogeneity + Additivity
Example for Liner Elements: Resistors, Inductors, capacitors, etc.
Example for Nonlinear Elements: Diodes, Transistors, etc

11. Lumped and Distributed Elements
When the voltage across and current through the element don’t vary with
dimension of the element, it is called lumped circuit elements.
Examples: Resistor connected in any electrical circuit.
When the voltage across and current through the element change with
dimensions of the element, it is called distributed circuit element.
Examples: Resistance of a transmission line. It varies with the length of the
line.

12. Uni Lateral and Bi lateral Elements
The unilateral circuit element does not offer same resistance to the
current of either direction. The resistance of the unilateral circuit element
is different for forward current than that of reverse current.
Examples: diode, transistor etc.
Conduction of current in both directions in a circuit element with same
magnitude is termed as a bilateral circuit element
It offers some resistance to current flow in both directions
Examples: Resistors, inductors, capacitors etc.

13. Passive Elements
• Resistor
A passive electrical component with two
terminals that are used for either limiting or
regulating the flow of electric current in electrical
circuits.
• Symbol:
• Represented with a letter “R”
• Units: OHM

14. Types of Resistors

15. Resistor Symbol