EE2010 Fundamentals of Electric Circuits

Text Book:Introductory Circuit Analysis

- Robert Boylestad

Course Description

– Basic circuit elements and concepts. – Basic laws of circuit theory: Ohm's law, Kirchoff's

laws. – Circuit theorems: superposition principle,

Thevenin and Norton theorems; maximum power transfer theorem.

– Techniques of circuit analysis: nodal and mesh analysis; sinusoidal sources and the concept of phasor in circuit analysis.

– Introduction to concept of active, reactive, complex power and power factor.

The Purpose of this CourseBy the end of this course the student will be able to • Identify and apply the concepts of DC electrical current,

voltage, power, resistance, capacitance and inductance. • Analyze series, parallel and combination circuits using

Ohm’s law, Joule’s law, Kirchhoff’s laws, Voltage Divider rule, Current divider rule, Mesh and nodal analysis.

• Analyze series-parallel circuits, including bridge networks, using Thevenin, Norton, Superposition, and Maximum power Transfer.

• Analyze the transient response of circuits with capacitors and inductors. Identify the parameters in sinusoidal AC waveforms.

• Implement and test DC circuit analysis.

EE2010 Fundamentals of Electric Circuits

Lecture - 1

Basic circuit elements and concepts

Atoms and their structure

electron

neutron

proton

Have neutrons, protons, and electrons.Protons are positively chargedElectrons are negatively charged

Electrons…Are located on the outer edges of atoms…they

can be moved.A concentration of electrons in an atom

creates a net negative charge.If electrons are stripped away, the atom

becomes positively charged.

Atomic Structure

The charge of electron is so small (- 1.602 x 10-19 C )• Charge in motion represents a current• Charge on a proton = 1.602 x 10-19 C

The Unit of Charge = Coulomb (C) 1 Coulomb of Charge is 1/ 1.602 x 10-19

= 6.242 x 1018 electronsThe symbol for charge is Q (or) q

Coulomb’s Law Like charges repel, opposites attract

9

What is an electric current?An electric current is a flow of microscopic particles called

electrons flowing through wires and components.

+ -

In which direction does the current flow?

from the Negative terminal to the Positive terminal of a cell.

Current

• The flow of electron in a conductor is called electric current

• The electric current (I) is defined as the time rate of change of charge I = dq/dt or I = Q/t

1 Ampere = 1 Coulomb / 1 Second• I = Q/t• Q = I x t• t = Q/I

2 types of current

• Direct Current (DC) – Where electrons flow in the same direction in a wire.

• Alternating Current (AC) – electrons flow in different directions in a wire

12

Question If a laptop constantly needs 2 Amps current from a

battery, how many electrons are drained from the battery in one hour?

1 Amp = 6.242 x 1018 electrons/second 2 Amp = 12.484 x 1018 electrons/second In one hour - > 3600 x 12.484 x 1018 electrons Answer is 4.49 x 1022 electrons

VoltageElectric Potential• The ability of a charged particle to do the work is called as

electric potential• The potential difference between two points in an electric

circuit called voltage• The unit of voltage is volt (V)• Electric potential (V) = work done/charge V = W/Q v = dw/dq 1 volt = 1 joule/coulomb• Voltage or potential difference is the energy required to move a

unit charge through an element

Resistance

• Resistance is proportional to length• Resistance is inversely proportional to the

cross sectional area R = ρ L/Aρ is the resistivity of the material (Ohm-Metres)

length

direction of current flow

Resistors, Capacitors and Inductors

• Resistors provide resistance– they oppose the flow of electricity– measured in Ohms ()

• Capacitors provide capacitance– they store energy in an electric field– measured in Farads (F)

• Inductors provide inductance– they store energy in a magnetic field– measured in Henry (H)