EECS 215: Introduction to Circuits - Faculty Server Contact
2-D Array of a Liquid Crystal Display 1. WAVES & PHASORS Applied EM by Ulaby, Michielssen and Ravaioli
Chapter 1 Overview Examples of EM Applications Dimensions and Units
Fundamental Forces of Nature Gravitational Force
Force exerted on mass 2 by mass 1 Gravitational field induced by mass 1 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 ~ 6.241 x 1018 electrons The coulomb is named for a French physicist, Charles-Augustin de
Coulomb (1736-1806), who was the first to measure accurately the forces exerted between electric charges. Charge of an electron e = 1.602 x 10-19 C
Charge conservation Cannot create or destroy charge, only transfer
Electrical Force Force exerted on charge 2 by charge 1 Electric Field In Free Space
Permittivity of free space 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: 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: 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.
Material Properties Traveling Waves
Waves carry energy
Waves have velocity Many waves are linear: they do not affect the passage of other waves; they can pass right through them Transient waves: caused by sudden disturbance
Continuous periodic waves: repetitive source Types of Waves Sinusoidal Waves in Lossless Media
y = height of water surface x = distance Phase velocity If we select a fixed height y0 and
follow its progress, then = Wave Frequency and Period Direction of Wave Travel
Wave travelling in +x direction Wave travelling in x direction +x direction: if coefficients of t and x have opposite signs
x direction: if coefficients of t and x have same sign (both positive or both negative) Phase Lead & Lag Wave Travel in Lossy Media
Attenuation factor xample 1-1: Sound Wave in Water Given: sinusoidal sound wave traveling in
the positive x-direction in water Wave amplitude is 10 N/m2, and p(x, t) was observed to be at its maximum value at t = 0 and x = 0.25 m. Also f=1 kHz, up=1.5 km/s.
Determine: p(x,t) Solution: The EM Spectrum Tech Brief 1: LED Lighting
Incandescen ce 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
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 Tech Brief 1: LED Basics Tech Brief 1: Light Spectra
Tech Brief 1: LED Spectra Two ways to generate a broad spectrum, but the phosphorbased approach is less expensive to fabricate because it requires only one LED instead of three
Tech Brief 1: LED Lighting Cost Comparison Complex Numbers We will find it is useful to represent sinusoids as complex
numbers z x jy z z z e j Rectangular
coordinates Polar coordinates j 1 Re z x
Im( z ) y Relations based on Eulers e j cos j sin
Identity Relations for Complex Numbers Learn how to
perform these with your calculator/com puter 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 Phasor Domain
Phasor counterpart of 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 Phasor Relation for Resistors Current through resistor
Time Domain Frequency Domain Time domain i I m cos t
iR RI m cos t Phasor Domain V RI m Phasor Relation for Inductors
Time domain Phasor Domain Time Domain Phasor Relation for Capacitors
Time domain Time Domain Phasor Domain
ac Phasor Analysis: General Procedure Example 1-4: RL Circuit Cont.
Example 1-4: RL Circuit cont. Tech Brief 2: Photovoltaics Tech Brief 2: Structure of
Q point of amplifier—importance in design of amplifier . Amplifier can amplify input signal faithfully if dc biasing circuit is selected properly. Dc biasing circuit decides voltage and currents in the amplifier circuit under no signal condition.
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