This document provides an introduction to electromagnetics for engineers. It discusses key topics including:
- Electromagnetic waves are created from vibrations between electric and magnetic fields. Examples include radio waves, light, x-rays.
- Dimensions and units - electromagnetic waves are measured in meters. Fields have both magnitude and direction.
- Wave characteristics such as amplitude, wavelength, frequency, and speed.
- Electric and magnetic fields - Coulomb's law describes electric forces, magnetic poles always occur in pairs.
- Frequency, time period, and angular velocity equations. Phasors represent waves using complex numbers.
2. Introduction
Electromagnetic waves or EM waves are waves that are created as a result of vibrations
between an electric field and a magnetic field.
A changing magnetic field will induce a changing electric field and vice-versa. These
changing fields form electromagnetic waves. Magnetic and electric fields of an
electromagnetic wave are perpendicular to each other and to the direction of the wave.
Examples of electromagnetic waves include radio waves, microwaves, infrared, visible light,
ultraviolet, x-rays, and gamma rays.
3.
4.
5. Dimensions, Units and Notation
Dimension for electromagnetics wave is length, and unit for EM is meter.
EM has scalar and vector quantities. It consists of a magnitude (scalar) and a direction, with the
direction usually denoted by unit vector.
6. Wave Characteristics:
•Amplitude: maximum displacement or height of a wave from its equilibrium position.
•Wavelength: the distance between two consecutive points that are in phase with each other
on a wave.
•Frequency: the number of complete wave cycles (oscillations) that pass a given point in one
second.
•Speed: the rate at which the wave propagates through a medium.
7.
8. ELECTROMAGNETISM
Electric fields
◮ Coulomb’s Law state that:
(1) two like charges repel one another,
whereas two charges of opposite polarity
attract,
(2) the force acts along the line joining the
charges, and
(3) its strength is proportional to the product
of the magnitudes of the two charges and
inversely proportional to the square of the
distance between them.
Magnetic fields
◮ The attraction–repulsion property for
magnets is similar to the electric force
between electric charges. However, magnetic
poles always exist in pairs while electric
charges can be isolated.
The electromagnetic force consists of an electrical component and a magnetic component.
9.
10. The frequency of a sinusoidal wave, f , is the reciprocal of its time period T:
Combining the preceding two equations yields
11. Phasors are mathematical representations used to analyze and describe the behavior of
waves, particularly in electrical engineering and physics.
•Phasors are often represented as complex numbers.
•Complex numbers consist of a real part (horizontal axis) and an imaginary part (vertical
axis).
12. where ω is the angular velocity of the wave and β is its phase constant (or wavenumber), defined
as
14. Your best quote that reflects your
approach… “It’s one small step for
man, one giant leap for mankind.”
- NEIL ARMSTRONG
Editor's Notes
Both electricity and magnetism can be static (respectively, what holds a balloon to the wall or a refrigerator magnet to metal), but when they change or move together, they make waves.
