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# Chapter 12 - PowerPoint PPT Presentation

Chapter 12. Thevenin, Norton and Maximum Power Transfer Theorems. Thevenin’s Theorem. Why Thevenin’s Theorem is useful. What is Thevenin’s Theorem?.

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Presentation Transcript

### Chapter 12

Thevenin, Norton and Maximum Power Transfer Theorems

• Why Thevenin’s Theorem is useful

• Everything in the original circuit, except the load, maybe replaced by an equivalent circuit. The equivalent circuit consists of a series combination of a voltage source and a resistance.

Write these on white board

Calculating RTHEVENIN (RTH)

RTH = 5kΩ

Calculating VTHEVENIN (VTH)

VTH = 10V

Now you can place any load in the circuit you want and the calculations are EASY!

.66mA

=10kΩ

Determine VTH

Solving for VTH

10V

5V

VTH = VA – VB = 5V

Determine RTH

What is the resistance from point a to b?

A

Turning Figure 12.15C into Figure 12.15D

10kΩ

9kΩ

10kΩ

3kΩ

• Everything in the original circuit, except the load may be replaced by an equivalent circuit. The equivalent circuit consists of a parallel combination of a current source and a resistance.

What a Norton Circuit Looks Like

Norton

Resistance

Norton Current IN

2mA

• There are a bunch of rules for how to calculate the Norton Current and Norton Resistance. However, a shortcut is to find the Thevenin Equivalent circuit and then convert it to a Norton

• Besides using traditional circuit analysis using Ohm’s Law, or Superposition, Mesh Analysis, Thevenin’s Theorem, and Norton’s Theorem, there are other circuit analysis techniques. A couple include:

• Nodal Analysis and Millman’s Theorem

Do more hw problems from back of chap 12 (9, 10, 11, or 12) if time

• In the following circuit solve for VTH, RTH, IN, RN, IL and VL

Solve for VL using traditional Ohm’s Law technique, Mesh Analysis, and Thevenin Analysis

• See notes

What load resistor would you use for the following circuit to have max power transferred?

?

What circuit analysis technique can we use to solve for this?

Thevenin’s Theorem. RTH = 5kΩ

I’ve checked this technique using Ohm’s law and it works. See following numbers:

5mW @ 5kOhm

4.94mW @ 4kOhm

4.96mW @ 6kOhm

A Couple Thoughts From to have max power transferred?Chapter 13

Stranded Wire vs. Solid Wire to have max power transferred?

Switches to have max power transferred?

SPST SPDT DPST DPDT