Superposition

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Superposition

• Lecture 4

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What did you learn from the notes?

• What were the main ideas in the notes?
• What concepts did you not understand?

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What did you learn from you notes?

• that all circuits cannot be solved with simple
  approaches and more formal methods are sometimes
  needed
• superposition is one such theorem
• you now can use node or mesh or superposition to
  solve the circuits

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Sample Problem
40 Ohms
80 Ohms
50 V
200 V
80 Ohms
Find the voltage across the resistor in black
using Superposition
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Kill Source 1
40 Ohms
80 Ohms
50 V
Short circuit
80 Ohms
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Solve for V across Rblack

• You can do this by combining the resistors in
  parallel (40 Ohms) and then using the voltage
  divider equation
• Answer 25 Volts

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Kill Source 2
40 Ohms
80 Ohms
Short circuit
200 V
80 Ohms
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Solve for V across Rblack

• You can do this by combining the resistors in
  parallel (26.6) and then using the voltage
  divider equation
• Answer ? 50 Volts

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Combine 2 Answers

• Using Superposition
• Answer 25 50 75 Volts

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Problem to Do Now
12 A
100 Ohms
Find the voltage across the resistor in black .
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Partial Solution

• Kill each source individually
• Killing current gt 10 V across it
• Killing voltagegt 3 amps flows through 100 Ohms
  gt 300 V across it
• A total of 310 V across it

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Problem to Do Now
12 A
100 Ohms
Find the voltage across the resistor in black
using mesh and node.
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Summary?

• Which of the three methods do you find easiest?
• What concepts do you find difficult to understand?