Circuit Theory/Superposition

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Goal[edit]

Split multisource circuit into smaller, simpler circuits, compute current or voltage and add.

Procedure[edit]

Pick one source, turn off all or set to zero all others:

  • Set Voltage Sources to V=0, doesn't care about current so is a short
  • Set Current Sources to I=0, doesn't care about the voltage so turns into an open

Example 1[edit]

Find the current through the 3 ohm resistor assuming moving left to right is positive:

The total current in the direction shown on the original diagram is going to be: \frac{24}{5} - \frac{14}{5} - \frac{3}{5} = \frac{7}{5} amp

Example 2[edit]

Find the current through the 4 ohm resistor assuming moving left to right is positive:

i = 35/3 - 11/36 + 25/18 = 51/4 = 12.75 amps

Simulation at circuit lab confirms the answer:

DC Simulation at Circuit Lab