http://img166.imageshack.us/img166/8658/...
I have the answers for a verification...
VAB=Vth=2,8V
Then answers to RAB=Rth=3,1 kĻ¸, VL=1,38V
My problem is after i have summed up all the resistors how do i calculate Vth,Rth and finally VL
Explain simplest way you can...thanks.Last question first: This is two voltage dividers with a load resistor connected between them. Thinking of this way makes the analysis very simple. This is also called a "Wheatstone bridge" if you care.
Remove the center resistor in your mind. Now you need to find the open circuit voltage. You can compute that by analyzing the voltage dividers but you ought to know that Vo=VinR2/(R1+R2) so: 5K and 4.7K with 15V in gives you 7.3V at point B.
The other pair gives you 10.3V at point A. So the voltage is 10.3-7.3 =3V.
Next short your Voltage and compute the resistance. You have 1k || 2.2k and 5k || 4.7k (the || means in parallel) which is 687 ohms and 2.4K. Those in series is about 3.1K
Not sure where you got 2.8V. Are you sure that's right (on the other hand, it is early here).
So Vth=3V, Rth=3.1k, Now it is easy to find Vl by the voltage divider on 3.1K and 3K and Vth. 3 (3k/(3.1k+3k)) = 1.48V
I think your "answers" might be off.