Circuit Theory/Superposition

Goal

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

Procedure

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

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: ${\displaystyle {\frac {24}{5}}-{\frac {14}{5}}-{\frac {3}{5}}={\frac {7}{5}}amp}$

Example 2

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

${\displaystyle i=35/3-11/36+25/18=51/4=12.75amps}$

Simulation at circuit lab confirms the answer: