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Maximum Power Transfer

Problem-Solving Strategy for solving the Maximum Power Transfer

STEP 1. Maximum power transfer takes place when the load resistance $R_L = R$.

PROBLEM:

Basic Engineering Circuit Analysis Problem 5.123
Note: This post is based on Irwin's Basic Engineering Circuit Analysis 11th ed. 
If there are any errors in solution, please let me know in the comments

SOLUTION:

Circuit with open circuit voltage
At first, we can find $V_x$ from $2mA$ source.

$\frac{V_x}{1k}=-2mA$, $V_x=-2V$

Then we can apply KCL on the top of node.

$\frac{V_{oc}+10}{2k}+\frac{V_{oc}+2}{1k}=2mA$
$V_{oc}=-\frac{10}{3}V$
Circuit with short circuit current
To find $V_x$, we can apply KCL on top of the node.

$\frac{V_{x}+12}{2k}+\frac{-V_{x}}{1k}+\frac{V_{x}}{1k}=0$
$V_x=-12V$

So $I_{sc}=2mA+\frac{-12}{1k}=-10mA$.

$R_{Th}$ is the ratio of $V_{oc}$ to $I_{sc}$.

$R_{Th}=\frac{V_{oc}}{I_{sc}}=\frac{1}{3}k\Omega$
Equivalent circuit for examining maximum power transfer


$R_L=R_{Th}=\frac{1}{3}k\Omega$ for maximum power transfer. Thus, the maximum power transferred to the load is

$P_L=\frac{V_L^2}{R_L}=\frac{25}{3}mW$

Related posts: Thevenin's Theorem
                   Norton's Theorem

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