1. EKT 242/3 & EKT 241/4 1. INTRODUCTION
Ruzelita Ngadiran

2. Chapter 1 Overview Electrostatic vs magnetostatic EM applications
EM Timeline
Dimensions & Unit
Fundamental Forces of Nature
The EM spectrum
Complex number (Revision)

3. objectives

4. Electrostatic vs. Magnetostatic
Fields arise from a potential difference or voltage gradient
Fields arise from the movement of charge carriers, i.e flow of current
Field strength:
Volts per meter (V/m)
Amperes per meter (A/m)
Fields exist anywhere as long as there was a potential difference
Fields exist as soon as current flows
We will see how charged dielectric produces electrostatic fields
We will see how current flows through conductor and produces magnetostatic fields
Example of electrostatics: vigorously rubbing a rubber rod with a piece of fur and bring to a piece of foil – foil will be attracted to the charged rod
Example of magnetostatics:
Current passes through a coil produces magnetic field about each turn of coil – combined will produce two-pole field, south & north pole

5. Examples of EM Applications

6. Dimensions and Units

10. Fundamental Forces of Nature

11. Gravitational Force Force exerted on mass 2 by mass 1
Gravitational field induced by mass 1

12. Charge: Electrical property of particles
Units: coulomb
One coulomb: amount of charge accumulated in one second by a current of one ampere.
1 coulomb represents the charge on ~ x 1018 electrons
The coulomb is named for a French physicist, Charles-Augustin de Coulomb ( ), who was the first to measure accurately the forces exerted between electric charges.
Charge of an electron
e = x C
Charge conservation
Cannot create or destroy charge, only transfer

13. Electrical Force
Force exerted on charge 2 by charge 1

14. Electric Field In Free Space
Permittivity of free space

15. Electric Field Inside Dielectric Medium
Polarization of atoms changes electric field
New field can be accounted for by changing the permittivity
Permittivity of the material
Another quantity used in EM is the electric flux density D:

16. Magnetic Field
Electric charges can be isolated, but magnetic poles always exist in pairs.
Magnetic field induced by a current in a long wire
Magnetic permeability of free space
Electric and magnetic fields are connected through the speed of light:

17. Static vs. Dynamic
Static conditions: charges are stationary or moving, but if moving, they do so at a constant velocity.
Under static conditions, electric and magnetic fields are independent, but under dynamic conditions, they become coupled.

18. Material Properties

19. The EM Spectrum

21. Tech Brief 1: LED Lighting
When a voltage is applied in a forward-biased direction across an LED diode, current flows through the junction and some of the streaming electrons are captured by positive charges (holes). Associated with each electron-hole recombining act is the release of energy in the form of a photon.
Incandescence is the emission of light from a hot object due to its temperature
Fluoresce means to emit radiation in consequence to incident radiation of a shorter wavelength

22. Tech Brief 1: LED Basics

23. Tech Brief 1: Light Spectra

24. Tech Brief 1: LED Spectra
Two ways to generate a broad spectrum, but the phosphor-based approach is less expensive to fabricate because it requires only one LED instead of three

25. Tech Brief 1: LED Lighting Cost Comparison

26. Complex Numbers
We will find it is useful to represent sinusoids as complex numbers
Rectangular coordinates
Polar coordinates
Relations based on Euler’s Identity

27. Relations for Complex Numbers
Learn how to perform these with your calculator/computer

29. Phasor Domain 1. The phasor-analysis technique transforms equations
from the time domain to the phasor domain.
2. Integro-differential equations get converted into
linear equations with no sinusoidal functions.
3. After solving for the desired variable--such as a particular voltage or current-- in the phasor domain, conversion back to the time domain
provides the same solution that would have been obtained had
the original integro-differential equations been solved entirely in the time domain.

30. Phasor Domain
Phasor counterpart of

31. Time and Phasor Domain
It is much easier to deal with exponentials in the phasor domain than sinusoidal relations in the time domain
Just need to track magnitude/phase, knowing that everything is at frequency w

32. Phasor Relation for Resistors
Current through resistor
Time domain
Time Domain
Frequency Domain
Phasor Domain

33. Phasor Relation for Inductors
Time domain
Phasor Domain
Time Domain

34. Phasor Relation for Capacitors
Time domain
Time Domain
Phasor Domain

35. ac Phasor Analysis: General Procedure

36. Example 1-4: RL Circuit
Cont.

37. Example 1-4: RL Circuit cont.

40. Tech Brief 2: Photovoltaics

41. Tech Brief 2: Structure of PV Cell

42. Tech Brief 2: PV Cell Layers

43. Tech Brief 2: PV System

44. Summary