1. Thevenin, Norton and Maximum Power Transfer Theorems
Chapter 12
Thevenin, Norton and Maximum Power Transfer Theorems

2. Thevenin’s Theorem
Why Thevenin’s Theorem is useful

3. What is Thevenin’s Theorem?
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.

4. Steps to make a Thevenin Circuit
Write these on white board

5. Calculating RTHEVENIN (RTH)
RTH = 5kΩ

6. Calculating VTHEVENIN (VTH)
VTH = 10V

7. Equivalent Thevenin Circuit
Now you can place any load in the circuit you want and the calculations are EASY!
=10kΩ
.66mA

8. Using the Thevenin Theorem
Determine VTH
Solving for VTH
10V 5V
VTH = VA – VB = 5V

9. Using the Thevenin Theorem
Determine RTH

10. Solving for RTH
What is the resistance from point a to b?

11. Turning Figure 12.15C into Figure 12.15D
10kΩ
9kΩ B A
10kΩ
3kΩ

12. Using the Thevenin Theorem

13. Final Thevenin Circuit (with load)

14. One more Thevenin Circuit Problem

15. Random Video of the Day

16. Norton’s Theorem
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.

17. What a Norton Circuit Looks Like
Resistance
Norton Current IN
2mA

18. Norton Shortcut
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

19. Using Norton Shortcut
2mA

20. Norton Example

21. Other Circuit Analysis Techniques
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

22. Practice Problem
In the following circuit solve for VTH, RTH, IN, RN, IL and VL

23. Another Practice Problem
Solve for VL using traditional Ohm’s Law technique, Mesh Analysis, and Thevenin Analysis

24. Maximum Power Transfer
See notes

25. RL (Ω)0
VT (V)
I (A)
PL(W)
Pi (W)
PT (W)
Eff (%) 20
2000 1
16.7
278.9
1394
1673.4 2
28.6
14.3
409
1022
1431.5 3
37.5
12.5
468.8
781.3
1250.1 4
44.4
11.1
492.8
616.1
1108.9 5 50 10
500
1000 6
54.5
9.1
496
414.1
910.05 7
58.3
8.3
483.9
344.5
828.35 8
61.6
7.7
474.3
296.5
770.75 9
64.3
7.1
465.5
252.1
717.55
66.7
6.7
446.9
224.5
671.35 80
320
400 30
85.7
2.9
248.5
42.05
290.55 40
88.9
2.2
195.6
24.2
219.8
90.9
1.9
172.7
18.05
190.75

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

27. 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
5kOhm
4kOhm
6kOhm
I’ve checked this technique using Ohm’s law and it works. See following numbers:

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

29. A Couple Thoughts From Chapter 13

30. Resistance Varies on Length, Diameter and Material

32. Stranded Wire vs. Solid Wire

33. Switches
SPST SPDT DPST DPDT