Intro to Electrical Engineering

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mechtech2081
ID:
107260
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Intro to Electrical Engineering
Updated:
2011-11-13 10:46:20
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Electrical Engineering Circuits Network
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Intro to Electrical Engineering
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  1. Volt
    Work per unit charge - (difference in potential energy)

    V = 1J/C = (1 kg·m2/s2)/C

    V = IR
  2. Coulomb
    Measure of charge

    1C = 1 A*s
  3. Joule
    Work to move 1 Newton 1 meter.

    1J = 1 kg·m2/s2
  4. Resistance
    Measure opposition to the passage of current.

    R=l/σA
  5. Power (P)
    • P = VI
    • = I2R
    • = V2/R
  6. Charge for Electron
    qe = -1.602*10-19 C
  7. Charge for Proton
    qe = 1.602*10-19 C
  8. Electric Current
    i = Δq/ΔT

    units: 1C/s
  9. Kirchoff's Current Law
    charge is conserved
    i = i0 + i1 + in
  10. Ohm's Law
    V = IR

    Conductance

    I=GV G: element
  11. Equivalent series resistance
    Resistors appear as a single equivalent resistance of value Req.

    Req = R1 + R2 + R3
  12. Voltage Divider
    When source voltage is divided among the resistors.

    Vn = (Rn/(R1 + R2 + Rn)) x vs
  13. In Series
    Circuit elements are in series when identical current flows through each element.
  14. In Parallel
    Circuit elements are in parallel when identical voltage flows through each element.
  15. Max current
    is = Vs/rs

    rs : resistance
  16. i(t) = Vs(t) / R
  17. Short Circuit
    Circuit element with resistance approaching zero.

    R = 0
  18. Open Circuit
    Circuit element with resistance approaching infiinty.

    R = infinity
  19. Loop
    any closed connection of branches.
  20. Mesh
    A loop that does not contain other loops.
  21. Node Voltage Method
    i = (va-vb)/R
  22. Principle of Superposition
    i = (vB1 + vB2)/R
  23. Thevenin Equivalent Circuit
    Represented by voltage source vT in series with RT (equibalent resistance).
  24. Norton Equivalent Circuits
    Represented by voltage current source iN in parrallel with RN.
  25. Method for solving Thevenin & Norton Req.
    • 1. Remove load
    • 2. Zero all independent voltage and current sources
    • 3. Compute total resistance with load removed

    RT = RN
  26. Method to compute Thevenin voltage
    • 1. Remove the load
    • 2. Define vOC across the open load termnials
    • 3. Apply any circuit analysis to solve vOC
    • 4. The Thevenin voltage is vT = vOC

    Thevenin voltage is vT = vOC
  27. Method to solve Norton Current
    • 1. Replace the load with a short-circuit
    • 2. Define the short-circuit current iSC = iN
    • 3. Apply any method to solve iSC
    • 4. Therefore iN = iSC

    Norton current = short-circuit current
  28. Ideal Capacitors
    Q = CV

    units : Farad -> C/V
  29. Capacitors in parallel
    Ceq = C1 + C2 + C3
  30. Capacitors in series
    1/(1/C1 + 1/C2 + 1/C3)
  31. Periodic Signal Waveform
    x(t) = x(t + nT) , n = 1,2,3
  32. Sinusoidal Waveforms
    x(t) = Acos(ωt) & Acos(ωt + Φ)
  33. Φ
    2π(Δt/T)
  34. phase shift
    Asin(ωt) = Acos(ωt - π/2)
  35. ω
    2πf
  36. Impedance of a resistor
    ZR(jω) = VS(jω) / I(jω) = R
  37. Impedance of an inductor
    ZL(jω) = VS(jω) / I(jω)= ωL∠π/2 = jωL
  38. Impedance of a capacitor
    • ZC(jω) = VS(jω) / I(jω)= 1ωC∠−π/2=−j / ωC
    • = 1 / jωC
  39. the impedance of a circuitelement
    Z(jω) = R(jω) + jX(jω)
  40. Circuit law for a capacitor.
    i(t) = C*(dv(t) / dt)
  41. Energy stored in a capacitor (J)
    WC(t) = 1/2*Cv2C(t)
  42. Voltage in an inductor.
    vL(t) = L*(diL / dt) units : 1 H = 1 V-s/A

    Inductors in series add. Inductors in parallel combine according to thesame rules used for resistors connected in parallel.
  43. Energy stored in an inductor (J)
    WL(t) = 1/2*(Li2L(t))
  44. e =
    cos θ + j sin θ
  45. Ae =
    Acos θ + jAsin θ = A∠θ
  46. Energy stored in steady state Capacitor

    Energy stored in steady state Inductor
    (1/2)*C*V2

    (1/2)*L*V2

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