Electric Circuit Class Discussions

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

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. 

• A technique called "Superposition" is used to solve for current flow through, and the voltage drop across, any impedance in a multiple source circuit.