Hi all,

Hope everyone's having a great weekend. I have a problem that I'm trying to solve and it's tripping me up. http://www.allaboutcircuits.com/worksheets/e_divide.html

It is Question 35 on the worksheet located at the link above. Since the problem states that you can assume there is a bleed current of 1.5 mA, I calculated the total current in the circuit to be 13.5 mA. I believe that this is what's throwing me off. Can someone tell me what the total current in the circuit is and how they calculated it?

Thanks!

 

To get I_total you simply need to add the load current plus the bleeding current.

 

Right, but for R3 + Load 1 you get 4.5 mA, which gives you the right answer for R3. But shouldn't the total of R2 + Load 2 give you 4.5 mA as well because of the loop rule?

 

There is 1.5mA through R3, 4.5mA through R2 and 16.5mA through R1, you know the voltages, V=IR and away you go.

 

I don't understand you problem
R2 = (9V - 4.8V)/4.5mA = 933.3

 

Ah, I see. Thank you. But how did you know to subtract 9 from 4.8 to get the voltage going through R2?

 

But how did you know to subtract 9 from 4.8 to get the voltage going through R2?

Because I know Ohm’s law and KVL/KCL all too well.
Simply Load 2 need 9V and Load1 needs 4.8V.
So the voltage drop across R2 must be equal 9V - 4.8V

 

Maybe this will help you withe KVL
And remember that if elements are connect in parallel they will have the same voltage across them.

VR4=V3+V2 or VR4=VB-V1, VR5=VB1, V1+V2=VR2

 

Thanks a lot guys. I need to practice my KVL/KCL, I'm so bad at them...