How can I come up with a equivalent resistance?

I

i55BaSH

Newbie
Joined
Dec 25, 2024
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Visit site
Activity points
29
Greetings,

I have the following circuits (picture attached):

V1 = 9 V
R1 = 1 kΩ
R2 = 7 kΩ
R3 = 7 kΩ
R4 = 0.7 kΩ
R5 = 1.5 kΩ
R6 = 1 kΩ



And I am trying to come up with an equivalent resistance so that I can calculate the voltage ( using the voltage divider formula ) at Node.

For the picture in the left I can come with an equivalent resistance:

Req_a = R3 and R4 in series as one
Req_b = Req_a and R2 in parallel as one
Req_c = Req_b and R5 in series as one

The final formula results ( under left picture ).
I have a big problem trying to come up with this approach on right picture.
Using the voltage divider formula, I just know that the equivalent resistance should be ~ 4133.6 Ω. Can you please help me?

Best regards,
 

Sort by date Sort by votes
You have the V applied to the entire network, and the current going into
it. So what is the Requiv of the entire Network ? E = I x R or R = ?

Then you have a R in series with the compound network, so now what
is Requiv of a series of two R's ? Rtotal = Rseries + Requiv .........
 

Upvote 0 Downvote
I am sorry but, I cannot follow you.

I just want to calculate the potential difference at Node ( green in pictures ) and for that I am using the voltage divider formula with R1 and a equivalent resistance.

V_Node = Req / ( Req+R1 )

In the left picture, for the red rectangle I managed to come up with a equivalent resistance for the entire block so that I can use the voltage divider formula.

In the right picture, I added the 6th resistor and I am stunned that I cannot come with the equivalent resistance for the entire orange block.

If it is not much to ask, can you help me with baby steps? Do I need to use Nodal Analysis? or is it there a method to compute a equivalent resistance for the orange block.
 

Upvote 0 Downvote
Hi,

what´s the exact question?
What values are given .. and what values do you need to calculate?

Something´s wrong with circuit#2. I guess there is a problem with one given value. Please check all numbers carefully.

Klaus
 

Upvote 0 Downvote
Hi Klaus,

At Node I want to calculate the potential difference using the voltage divider formula:

For circuit 1:

V_node = V1 * (Rb / (Ra+Rb)) -> where Ra = R1 and Rb is the equivalent resistance of R2, R3, R4, R5 as following:

(( R3 series R4 ) || R2 ) series R5

For circuit 2:

7.24V = 9V (Rb / (1kΩ+Rb))

using the voltage divider formula and knowing that on Node I have 7.24V it resulted Rb = 4133.6 Ohm as equivalent resistance.

But my question is:

How Do I arrange R2,R3,R4,R5,R6 so that it gives me that value? ( just like I explained for circuit one)
 
Last edited:

Upvote 0 Downvote
Upvote 0 Downvote


Are the currents and R values, as shown in right hand pic the "givens" ?

If so the node V is simply Vnode = 9V - 1.76 mA X R1.......

But to use V divider you need the equiv R at Vnode. Using above Vnode, and you know the total
current going into the complex part of the network, you have -

Requiv = Vnode/1.76 mA.....

But if you want to do the derivation of Requiv, FVM would be the way at getting at Requiv, has
the advantage of not needing any I's, just Vsource (9V).....
 

Upvote 0 Downvote
You must log in or register to reply here.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…