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by: Luca Tomescu

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# Intro to EE (EE 302) Exam #1 Study Guide EE 302

Marketplace > University of Texas at Austin > Electrical Engineering > EE 302 > Intro to EE EE 302 Exam 1 Study Guide
Luca Tomescu
UT

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This is the study guide for our first exam, which covers chapter 1 and 2 from the textbook, as well as all the material we covered in class up to (and including) September 19th.
COURSE
EE 302: Introduction to Electrical Engineering
PROF.
Jack C. Lee
TYPE
Study Guide
PAGES
5
WORDS
CONCEPTS
Electrical and Computer Engineering, Circuits, DC circuits
KARMA
50 ?

## Popular in Electrical Engineering

This 5 page Study Guide was uploaded by Luca Tomescu on Saturday September 24, 2016. The Study Guide belongs to EE 302 at University of Texas at Austin taught by Jack C. Lee in Fall 2016. Since its upload, it has received 74 views. For similar materials see EE 302: Introduction to Electrical Engineering in Electrical Engineering at University of Texas at Austin.

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Date Created: 09/24/16
Intro to Electrical Engineering (EE 302): Exam #1 Study Guide  Atoms o Based on the Rutherford Model from 1911 o Negatively charges electrons orbit a positively charged nucleus composed of protons and neutrons  Electron charge = -1.6E-19 C  Electron mass (m e = 10^-31 kg  Proton charge = +1.6E-19 C  Proton mass = 2000 x m e o Electrically neutral (#e = #p) o Positive ion (#e < #p) o Negative ion (#e > #p) o Ionization = process of gaining or losing electrons 15 o 7???? : Nitrogen with 7 protons + 8 neutrons = 15 amu  Charge o Movement of charge  current o Charged particles exert force on other charges (Coulomb’s Law) o Charge is quantized (there is a fundamental minimum nonzero magnitude o Charge is conserved in a closed system o Opposite attract, like charges repel o ???? = ????1 2 [Newtons] where ∈ = ∈ ∈???? 0 4????∈????  ∈ 0 permittivity of free space = 8.85E-19 [Farad]/[cm]  ∈ = relative permittivity (or dielectric constant) ????  Current o Net flow of positive charge across a cross-sectional area per unit time ???????? ????  ???? = [ ] ???????? [????????????] ???????? ???? o Example: 10^6 electrons in 1 picosecond 10 (1.6????−19)  10−12 = −0.16???? o To specify current:  1. Reference direction: we assign a current direction  2. Numerical value: magnitude of the current o Direct Current (DC)  i(t) = constant  DC conditions:  i = constant with time  V = constant with time o Alternating current (AC)  i(t) ≠ constant  i(t) = Acos(ωt + ϴ) o Convention:  I, V  DC condition  i, v  AC condition  Electric Field o Force per unit charge at a given point o E = ????1 [ ] 4????∈????2 ???? o Electric field is a vector  Energy o Energy = Force x distance = work done = [N*m] = [J] ???????? o ???? = ∫???????? ???? ???????? o W > 0, work is done by F o W < 0, work is done “against F”  Voltage (potential difference) o Voltage = work done per unit charge  Voltage always occurs between 2 points o [Joules/Coulomb] = [Volt] o Sign of voltage indicates direction (as with current)  Electric field ALWAYS goes in the direction of decreasing potential  i.e. +  -  Summary ???? ???? o ???? = ???? = ???? o ???? = ∫???? ???????? o ???? = ???? ????  Power o Power = work done per unit time = W/t o Power = voltage x current = VI  Passive sign convention o Current travels in the direction of decreasing potential (voltage) o P > 0  Energy is dissipated by a circuit device (recipient)  Resistor gives off heat  LED gives off light o P < 0  Energy is delivered by a circuit device (supplier)  Battery turns chemical energy to electrical energy o Circuits always have a “ground reference point”  The voltages are all in relation to this point  It’s often not shown; generally assumed to be the bottom-most node of a circuit  Circuit Elements (devices) o Battery, resistors, diodes, inductors, transistors, capacitors  Battery o Has constant voltage at any current  Resistor o Varies according to I = V/R (Ohm’s Law) o Slope shown as 1/R  As resistance increases, the slope becomes shallower o When R = 0, it is referred to as a “short circuit” o When R = infinity, it is referred to as an “open circuit” o R = V/I = [volt]/[amp] = [ohms]  Conductance o Conductance (G) = I/V = 1/R = [amp]/[volt] = [mho] = [siemens] o As conductance increases, the slope of the line becomes steeper  Ohm’s Law (ideal) o I = V/R o R = ρ x length/cross-sectional Area  Conductor: ρ < 10^-2 ohm*cm  Insulator: ρ > 10^5 ohm*cm  Semiconductor: 10^-2 < ρ < 10^5 ohm*cm o Voltage and current sources are Independent sources  Ideal voltage source has constant voltage for any current  Ideal current source has constant current for any voltage o Resistors  As temperature increases, so too does resistance  Higher temperature causes more scattering of electrons through a metal  Individual atoms vibrate in a phenomenon called “phonons” o Power and Ohm’s Law  P = IV = V^2/R = I^2 R  Independent Sources o Direct current  V(t) and I(t) = constant o Alternating current  v(t) and i(t) vary with time  Dependent Sources o Voltage or current sources whose magnitude depend on voltage or current in another part of the circuit o There are voltage-controlled voltage sources, current-controlled voltage sources, voltage-controlled current sources, and current-controlled circuit sources  All four are models for electronic devices (operational amplifiers, transistors, etc.)  Kirchhoff’s Law o Node = a point at which 2 or more circuit elements are connected o KCL: Algebraic Sum of all currents at any node at any time is 0  1. KCL = conservation of charge  2. Current entering the node is +, current leaving the node is –  Can be switched, as long as you’re consistent  3. Independent of the nature of the circuit elements  The number of independent KCL equations = n – 1  Where n = # of nodes o KVL: Algebraic sum of all the voltage around any loop (or closed path) at any time is 0  1. Independent of the characteristics of circuit elements  2. Analogy  Think of a roller coaster with constantly changing gravitational potential energy  Keep in mind that KVL is NOT conservation of energy o The analogy just provides an easier way of thinking about it  Parallel combination o Total voltage = V1 = V2 o Total current = I1 + I2 ????2  ????1= ????1+????2???????? ????1  ????2= ???????? ????1+????2  In a current divider, the individual current through each resistor is a fraction of the total current  i.e. You have to look at the OTHER resistor in parallel o Resistance  1 = 1 + 1 ???????????????????????? ????1 ????2 ????1 2  ???? ???????????????????????????????????????? ???? 1???? 2  Series combination o Total voltage = V1 + V2 ????  ????1= 1 ???????? ????1+????2  ???? = ????2 2 ????1+????2  Individual voltage is a fraction of total voltage o Total current = I1 = I2 o Resistance  ???? ????????????????????????????????????????= ???? 1 ???? 2  Know the transitions between Y and Δ equilateral circuits o Check your notes since I can’t exactly draw those here o You could likely figure these pretty easily without the equations as well  Power in circuits o Sum of the power of each circuit element = 0  Conservation of energy!  Misc. Info from Practice problems o Know circuits with a source and load connected by a transistor o Having a dependent source on the load side helps avoid the “loading effect”  And the most important thing… o Do some practice exams from Canvas!!

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