I found this question difficult. Anyone know how to solve it?

[alternativess]

http://img385.imageshack.us/img385/7747/q64yw.jpg

[mdshunk]

Yes, I know how to solve it.

[Homer]

Yes, I know how to solve it.Me too! :D

You need to create a Thevenin equivalent circuit of the source (everything to the left of the load). Then if you make the load resistance equal to the Thevenin resistance you will get maximum power transfer.

Alternativess, how many more questions do you have for your homework assignment?

Homer

[alternativess]

That's the question that may come out in the final. Now I am going to find it out, could you please teach and make it clear? Thanks.

[Homer]

That's the question that may come out in the final. Now I am going to find it out, could you please teach and make it clear? Thanks.A thevenin circuit is just a single impedance (resistance in this case) in series with a voltage source (DC in this case).

You need to convert the entire circuit to the left of the load resistor to this.

The rules are to short out voltage sources (batteries) and open up current sources. So, your 15V supply is shorted and the 5mA supply is disconnected. Looking to the left from the load I see two resistors in parallel. A 2kΩ and a 6kΩ resistor that combine to 1.5kΩ.

The thevenin resistance is therefore 1.5kΩ. To find the thevenin voltage it's easiest to start with the short circuit current of the original circuit (RL = 0Ω). The short circuit current is 7.5mA. This is 5mA + 15V/6kΩ.

The thevenin voltage is therefore V = I x R = 7.5mA x 1.5kΩ = 11.25V

For maximum power transfer, the load resistance must equal the source or thevenin resistance. So Rload = 1.5kΩ.

Your equivalent circuit with the load is a voltage supply of 11.25V, a source resistor = 1.5kΩ and a load resistor = 1.5kΩ.

Iload = 11.25V/3kΩ = 3.75mA

Vload = 3.75mA x 1.5kΩ = 5.625V

Pload = 5.625V x 3.75mA = 21.1mW

Homer

[Ohm1]

I can see I've been missing out!

[alternativess]

Halo Homer, if the circuit looks like this which have the dependent source, I want to find the Thevenin equivalent circuit with respect to the terminal a,b for the circuit, how to solve it?


http://img139.imageshack.us/img139/7741/2222229ei.jpg
Can I still use the method short out voltage sources (a.c) and open up the dependence current sources? The dependent souces there really make me confused....

[K2eoj]

Yes, I know how to solve it.

Glad to see your alive MD. And well?? I wish I knew how to solve it. K2

[ggratecc]

Halo Homer, if the circuit looks like this which have the dependent source, I want to find the Thevenin equivalent circuit with respect to the terminal a,b for the circuit, how to solve it?


http://img139.imageshack.us/img139/7741/2222229ei.jpg
Can I still use the method short out voltage sources (a.c) and open up the dependence current sources? The dependent souces there really make me confused....

I didn't work on the original problem of the thread, however, when
alternativess posted this second circuit, I decided to give it a try.
Here is what I came up with...if there are any errors, please let me know.

Here is the link to my .pdf file on Geocities:
http://www.geocities.com/ggratecc/thevenin_dependent.pdf