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Reference Guide

Electrical Engineering - Reference Guides

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University of Akron
Electrical Engineering

l e a r n • r e f e r e n c e • r e v i e w permacharts TM Electrical Engineering GLOSSARY OF TERMS MECHANICS FUNDAMENTALS Conductor Material which permits electrons to flow freely NEWTON’S LAWS OF MOTION Couple Two equal and opposite parallel forces that are applied to the same body Law I Bodies will continue in uniform motion unless acted upon by external forces Dielectric Insulating material between capacitor plates; Law II The rate of change of a body’s linear momentum is capacitance increases by numerical factor, k proportional to, and in the direction of, force applied (dielectric constant) • F = ma Electric Measure of the opposition that an electric Impedance circuit presents to the flow of current when Law III Forces of action and reaction between bodies are equal voltage is applied in magnitude, opposite in direction, and collinear Electromagnetic Oscillations of the inductor’s magnetic CONDITIONS OF EQUILIBRIUM Oscillation field and the capacitor’s electric field EMF Device Works on charges to maintain a potential • Static equilibrium occurs when the resultants of all external forces difference between output terminals acting on a body are zero Equipotential Adjacent points on a surface with the same Equilibrium Equations Surface electric potential; electric field is always perpendicular to equipotential surfaces Note: Equations are for planar, 2-dimensional, and 3-dimensional Ferromagnetic Substance in which magnetization persists rigid body statics Material after the field has been removed • Vector relationships for a force system: ∑ F = 0 and ∑ M = 0 Force Vector action of one body on another • Written as components along x-, y-, and z-axes, relationships Hysteresis Residual magnetism that is left when the become ∑ Fx= 0, ∑ y = 0, ∑zF = 0, x M = 0, y M = 0, and material (such as iron) is slowly demagnetized ∑ Mz= 0 Inertia An attribute of bodies implying capacity to GEOMETRY OF MOTION resist changes of motion Insulator Material that impedes conductance of • In mechanics, kinematics is the study of the motions of bodies as electricity a function of time Integrated Complete circuit is contained in a single piece Linear All points of a body follow congruent paths Circuit of semiconductor material Rotational Paths circle about an axis; velocity and acceleration Magnetic Simplest magnetic structure (such as a bar are proportional to the radius Dipole magnet) where net magnetic flux is zero w Mesh In circuit analysis, a loop that has no loop in Harmonic Body moves back and forth about a position at rest Oscillation (amplitude represents maximum deflection) w its interior Base Derivatives of Kinematics Momentum An attribute that is proportional to the mass w and velocity of a body Velocity ds Where s represents distance and Open Circuit Path for current flow between 2 points is v = dt t represents time . broken p e Phasor A vector that rotates around an origin Angular dφ Where f represents the angle Principle In a circuit network, a node (junction) with Velocity ω = dt r Node three or more branches m Reactance Circuit property with capacitance and Angular a =d ω Where w represents angular velocity inductance Acceleration dt a Rectification Changing AC to DC by blocking the reverse c flow of a charge MOMENTS OF INERTIA h Resonance An oscillation of a system at its natural • Define the relationship between the area or mass of a body and a frequency Semiconductor Material that is not conductive nor insulating the position of a line r • Moment of inertia of a figure = sum of moments of its parts t Shearing Force In mechanics, a force acting parallel to a Area Moments of Inertial, I (Statics)y plane Measuring 2 s Short Circuit Path for current flow between two points has the distribution A dx y∫ A . zero impedance 2 x dA c Stress In mechanics, the measure of internal forces of area about an axiA dy x∫ r y o of a body between particles resisting A dz r∫ 2 separation 0 x m Superconductor Material that presents no resistance to the movement of electric charge Mass Moments of Inertia, I (Dynamics) Torque Turning force or twisting moment Measuring the moment of inertia dm of a volummmdIrr= ∑ =2 ∫ Torsion Torque applied in planes perpendicular to body’s axis r Transformer Electromagnetic device with 2 or more mutually coupled windings; it can raise and lower voltage in a circuit 1 ELECTRICAL ENGINEERING • A-816-8 © 1996-2011 Mindsource Technologies Inc. l e a r n • r e f e r e n c e • r e v i e w permachartsM ELECTROSTATICS CIRCUIT BASICS ELECTRIC CHARGE, Q Circuits Made up of active and passive elements and their interconnecting conducting paths Elementary Charge Active Include sources such as batteries, DC generators, AC generators, and so on • Charge is not fluid; it consists of multiple elementary charges Elements • Any charge q can be written as q = ne, Passive Include current controlling devices such as resistors, capacitors, inductors, where n = positive or negative integer and Elements and so on e = elementary charge Note: e has a value of 1.602 ¥ 10C CIRCUIT ANALYSIS & DESIGN Electric Current (coulomb) Electrostatic Force Current The rate at which electricity flows Magnitude Depends on electromotive force (potential difference) and dimensions of • The charge on any body is measured in relation to the force between two charges path through which it circulates Force: Proportional to the product of the Ohm’s Law I = V/R, where I is the current, V is the electrical potential difference, and two charges; inversely proportional to the R is the resistance square of the distance between them Potential Difference (Electromotive Force, EMF) Coulomb’s Law • In the case of direct current, Ohm’s law defines potential difference as the product of • Relates force, quantity of charge, and current and resistance; commonly used as a measure of the strength of a source of distance of separation such that force electric energy (EMF); here, V = IR between 2 electric charges is p2oportional Resistance to product of22 charges ÷ distancer • Resistance is passive elements in circuits which control current and the degree to which F = q1 2/4πed Newtons a material resists the flow of current ELECTRIC FIELD, E • Used to control flow of current through a circuit; here, R = V/I Resistivity • Charged particles alter their surrounding space • Resistivity is property of a material determines its conductivity • The electric field (or field intensity) can be • To calculate resistance from resistivity, R = pl/A, where p is the resistivity of the material, l is the length, and A is the area found at a point by imagining a particle of charge at rest and measuring the electric force F acting upon it; KIRCHHOFF’S LAWS E = electrostatic force / charge • According to Gauss’ Law, the total electric Current Law Total current flowing into any node in a circuit equals the total current flux of a closed surface in an electric field is flowing away from that node • The algebraic sum of the currents proportional to the sum of the electric entering any node is zero • ∑ I = 0 charges within the surface Voltage Law In a closed circuit, sum of potential drops equals resultant EMF in the loop • The algebraic sum of the potential difference around any closed • Capacitance (C) is the property of an element which opposes changes in circuit is zero • ∑ V = 0 voltage, as given by the equation q = CV, m where q is the charge and V is the THEVENIN’S THEOREM NORTON’S THEOREM potential difference o • A network of sources and resistors at a • A network of sources and resistors at a • A capacitor consists of two isolated pair of terminals can be replaced with pair of terminals can be replaced by a c conductors (plates) with equal and opposite a series combination of a voltage parallel combination of a current source . charges (+q, -q) separated by a dielectric source and resistor and resistor s t r SELECTED QUANTITIES & UNITS a Base Quantities Common Quantities h Quantity Symbol Unit Unit Symbol Quantity Symbol Unit Unit Symbol c Length L, l meter m Charge Q, q coulomb C a Mass M, m kilogram kg Current I, I ampere A m Time T, t second s Potential difference volt V Electric current I ampere A Power P, p watt W r e Temperature Kelvin K Work/Energy W, w joule J Luminous intensity candela cd Resistance R ohm Ω p Plane angle radian rad Conductance ∑ siemens S . Solid angle steradian sr Capacitance C farad F w Magnetic flux F weber Wb Constants w Magnetic field B tesla T Constant Symbol Value Force F Newton N w Elementary charge e 1.60 ¥ 1019C -11 2 2 Flux density B tesla T Gravitational constant G 6.67 ¥ 10 Nm /kg Inductance L henry H Permittivity constant e 8.85 ¥ 1012F/m 6 Frequency ƒ hertz Hz Permeability constant µ0 1.26 ¥ 10 H/m Angular frequency w radians/second rad/s Electron mass m e 9.11 ¥ 1031kg Proton mass m 1.67 ¥ 1027kg Electromotive force EMF volt V p 2 ELECTRICAL ENGINEERING • A-816-8 © 1996-2011 Mindsource Technologies Inc. l e a r n • r e f e r e n c e • r e v i e w permachartsM E
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