# 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.
• 2. Zero all independent voltage and current sources
• 3. Compute total resistance with load removed

RT = RN
26. Method to compute Thevenin voltage
• 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

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

 Author: mechtech2081 ID: 107260 Card Set: Intro to Electrical Engineering Updated: 2011-11-13 15:46:20 Tags: Electrical Engineering Circuits Network Folders: Description: Intro to Electrical Engineering Show Answers: