# How to find the load resistor's resistance?

Use max power transfer theorem to calculate the value of RL for the following circuit.

I've done the Thevenin's equivalent circuit but from there I don't know how to find the $$\R_{Load}\$$. I need it to do a table of current and power against $$\R_{Load}\$$.

Any suggestions or help would be appreciated.

• I don't think you can "find" $R_{Load}$. You don't have a current or the voltage on $R_{Load}$, so I don't see any way for you to calculate $R_{Load}$. Is there some part of the assignment you haven't shared with us? – JRE Oct 10 '20 at 18:45
• the question is to make a Table of Current against Power like this electronics-tutorials.ws/dccircuits/dcp_9.html and i thought i would need the Rload to do it? – oritem8 Oct 10 '20 at 18:50
• Yes, you need $R_{Load}$ to figure out how much current flows through it and how much power it dissipates. I just don't think you have enough given information to calculate $R_{Load}$. You need one of the following: 1. Another given voltage. 2. A given current. 3. Given $R_{Load}$ – JRE Oct 10 '20 at 18:54
• Use max power transfer theorem to calculate the value of RL for the following circuit. (This is the question it that helps) – oritem8 Oct 10 '20 at 18:59
• @oritem8: That belongs in the question. That's the missing bit of information. – JRE Oct 10 '20 at 19:04

The "maximum power transfer theorem" tells you that for maximum power transfer, the load resistance must be the same as the source resistance.

You've used Thevenin's theorem to find the source resistancee. Given that and the statement above about the maximum power transfer theorem, you should be able to figure out $$\R_{Load}\$$ pretty easily.

From that you can find the current through the circuit and the current through $$\R_{Load}\$$.

With the current through $$\R_{Load}\$$, you can find the dissipated power using the formula for Joule heating. That's $$\P_{Load} = I_{Load}^2R_{Load}\$$

• @relayman357 Impedance is the correct term to use for general rule here – Tony Stewart EE75 Oct 10 '20 at 22:44

Zout = 3.61K +10 K therefore if a 13.61K load is applied, it will reduce the 4.xxx Vo in half.

You choose whatever load you need.

High Z for low voltage loss or matched Z for max power transfer.

• Did this not answer your question? – Tony Stewart EE75 Oct 10 '20 at 22:45