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This blog contains the summarized topics discussed in Electric Circuit 1.

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Week Eight: Thevenin's Theorem in AC Circuits

Sabado, Pebrero 21, 2015 | by Unknown

Thevenin Equivalent Circuit

  • Thévenin’s theorem, as stated for sinusoidal AC circuits, is changed only to include the term impedance instead of resistance.
  •  Any two-terminal linear ac network can be replaced with an equivalent circuit consisting of a voltage source and an impedance in series.
  • VTh is the Open circuit voltage between the terminals a-b.
  •  ZTh is the impedance seen from the terminals when the independent sources are set to zero.

Ex.1  Thevenin Equivalent At terminals a-b


Watch a Video using Thevenin's Theorem!


Reflection:
    The process used in AC analysis is the same with DC analysis. 


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Week Seven: Source Transformation on AC Ciruits

| by Unknown

Source Transformation

  • Transform a voltage source in series with an impedance to a current source in parallel with an impedance for simplification or vice versa.

Ex.1 Practice Problem 10.4: Calculate the current Io

If we transform the current source to a voltage source, we obtain the circuit shown in Fig. (a).
By current division,

Watch Another Example of Source Transformation.



Reflection:
   In AC analysis, we applied the same principles used in  source transformation from DC analysis. 


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Week Six: Superposition Theorem on AC Circuits

| by Unknown


  • A technique called "Superposition" is used to solve for current flow through, and the voltage drop across, any impedance in a multiple source circuit.
Follow these steps:
  1. Replace all but one of the voltage sources with a "short". Current sources are replaced with an "open". (All sources must have the same frequency.)
  2. Solve for the current or voltage flowing through each impedance.
  3. Select the next source and repeat until all sources have been used.
  4. Add all the currents or voltages for each impedance and label the original circuit.
Problem Example:


Please Watch:This video will provide you a further understanding of Superposition Theorem.


Reflection:
   The method used for using superposition theorem in AC circuits is still the same with DC circuits. The difference is that values may be given in complex or phasor form and sources are sometimes shown in different frequencies which requires you to convert them.



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Week Five: Sinusoidal Steady-State Analysis Part II

Lunes, Disyembre 22, 2014 | by Unknown

Mesh Analysis

          -The mesh current method of analyzing ac requires Kirchhoff's Voltage Law to sum ac voltages around a closed path in terms of the mesh (loops) current variables. The branch impedances are represented by complex numbers, each with a real part and an imaginary part. the real part represents the branch reactance.

Important Notes:

  • Just as in KCL, the KVL analysis also applies to phasor and frequency domain circuits.
  • The same rules apply: Convert to frequency domain first, then apply KVL as usual.
  • In KVL, supermesh analysis is also valid.

Example: Solve for Io:




For another Example, Watch this Video!


Reflection:
        In applying mesh analysis in ac, the process for solving an unknown are still identical. The only difference is that the values given may occur complex numbers and phasor form for sources. Sometimes, I fail to acquire the correct answer because I carelessly convert the values in their wrong convertion or equivalence. For me, I find mesh analysis more convenient than nodal analysis. But of course, it depends on the person employing which method is more suitable for him or her.

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Week Four: Sinusoidal Steady-State Analysis Part I

Sabado, Disyembre 6, 2014 | by Unknown

Nodal Analysis

  • Since KCL is valid for phasors, we can analyze AC circuits by NODAL analysis.

  • Practice Problem 10.1: Find v1 and v2 using nodal analysis
Solution:

For more information, Watch an Example!

Reflection:
        The application of nodal analysis in ac is still the same with the method used in dc. The difference between the two is that in ac analysis, it contains complex numbers and phasor forms. I still find it confusing when it comes to conversions. But with enough practice, anyone can attain the expected results.

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