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EEE 224 ELECTROMAGNETIC THEORY

METU -^ Introduction

NCC

Assist. Prof. Dr.

Özlem Özgün

Office

:^ S-

Phone

:^ 661 2972

E-mail

:^ ozozgun@metu.edu.tr

Web

:^ http://www.metu.edu.tr/~ozozgun/

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Time Schedule -

Grading Policy

Follow

METUONLINE

Monday^ for course materials and announcements!

Wednesday

Office Hours:

Monday & Tuesday (13.40 –

14.30) (or by appointment)

Grading:st^1 Midterm

: 25% nd^2 Midterm

: 25%

Final

: 35%

Quiz -

Attendance

: 15%

Homeworks will be collected, but not be graded and not be given back

.

Quiz questions might be chosen from the homework questions.

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Objective

Introduce the basic principles of electromagneticphenomena in terms of a few relatively-simple laws.

Gain physical

intuition about naturearound you

Gain physical

intuition about naturearound you

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Is Electromagnetics difficult?

Electric and Magnetic Fields

are vectors in 3D coordinate system.

Therefore

Æ Solution of electromagnetic problems requires abstract

thinking!

You

must develop a deep physical understanding

!

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Computer Technology

Electromagnetics is everywhere!

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Antenna Technology

Electromagnetics is everywhere!

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Biomedical Applications

EEG^

(Electroencephalography) measures

the

electrical activity

produced by the brain as

recorded from electrodes placed on the scalp.

Person

wearing electrodes for EEG

ECG^

(electrocardiogram) records the electrical activity of the heart over time.

Electromagnetics is everywhere!

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Research Areas of Electromagnetics

-^ Antennas •^ RF / Microwave •^ Computational Electromagnetics (Numerical Modeling) •^ Electromagnetic Scattering

& Propagation

-^ Radars •^ Remote Sensing •^ Optics •^ Etc…

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A fundamental conserved property of some subatomic

particles

(electron, proton, neutron). It exists because of an excess or a deficiency of electrons. Electron^

Proton^

Neutron

Varieties: Positive (+)

Negative (-)

Electrical charge exists in discrete quantities,which are integral multiples of the charge on anelectron

-e, e = 1.

×^10

-19^ (C)

6.24 x 10

18 electrons carry a charge of 1 coulomb On the macroscopic level, charge is assumed to be“continuous”^ Charge is conserved!

What is Charge?

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Charges create Electric and Magnetic Fields Separation of charges

Æ^

creates electric force (or voltage)

Electric field is force per unit charge.

+^

+^

_

Motion of charges

Æ^

creates electric flow (current)

Current creates magnetic field.

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Static or Dynamic Fields

Static :

(^0) = ∂ ∂^ t

Charges are at rest

(stationary)

OR in steady-motion

with constant velocity (DC current)

(no time-variation)

Dynamic Charges are in time-varying motion (accelerating or decelerating) (e.g., AC current)

:^

0 ∂^ ≠^ t ∂^

(time-varying)

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Fundamental Electromagnetic Field Quantities

ε^0

D =

E

G^

G

μ^0

B =

H

G^

G^

Constitutive relations in free-space

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0

10

(F/m)

ε^

−

≅^

×^7 0

4

10

(H/m)

μ^

π^

− ≅^

× Permittivity of free-space:^ Permeability of free-space:

Electric field intensity Electric flux density Magnetic flux density Magnetic field intensity

E D B H

V/m C/m

2

T A/m

Field Quantity

Symbol

Unit

Electric Magnetic

V/m = kg.m/A/s

3

C/m

2 = A.s /m

2

T (tesla) = Wb / m

2 = kg/A/s

3

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Maxwell’s equations

are the “complete”

laws to

describe an electromagnetic

phenomenon.

Maxwell’s Equations

James Clerk Maxwell (1831–1879) (British)

B^ t E^

∂− ∂

×∇

D

H^

J^

∂ t

∇ ×

=^

• ∂ D

∇ ⋅^

=^0 B ∇ ⋅^

=

Maxwell-Faraday’s Equation(Faraday’s law of induction)^ Ampere’s Law withMaxwell’s correction Gauss’

Law Gauss’

Law for magnetism

J^

ρ∂ t

∇ ⋅^

= −

∂^

Continuity equation (implicit in Maxwell’s eqn.s)

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Special Cases of Maxwell’s Equations

Electro-statics^ (Only E-field)

Maxwell’s Equations^ Magneto-statics

(Only H-field)

Electromagnetic Waves (Both E

& H-fields, coupled)^ Circuit^ Theory Dimension << Wavelength (

λ)

Statics :

(^0) = ∂ ∂^ t