# Find the resistance R in this network

• Engineering
• Edy56
In summary, the conversation is about a circuit problem and the person asking for help has not shown their work or calculations. They have described their steps, but have not provided any numbers or equations. Another user has suggested removing some components and provided the values for the resistors. They also have simplified the circuit and calculated the final equivalent resistance to be 3k. However, the original user has not responded with their calculations or whether this solution worked for them.

#### Edy56

Homework Statement
I am supposed to find the equivalent to R2 and I got 2, but I am supposed to get 3
Relevant Equations
None

Welcome to PF.

It's pretty hard for me to read your uploaded pictures. Can you post a better picture of the original circuit, and type some of your work into the forum so it's readable? Thanks.

(you should consider learning to post math using LaTeX -- see the "LaTeX Guide" link below the Edit window)

berkeman said:
It's pretty hard for me to read your uploaded pictures. Can you post a better picture of the original circuit, and type some of your work into the forum so it's readable? Thanks.

berkeman said:
Welcome to PF.

It's pretty hard for me to read your uploaded pictures. Can you post a better picture of the original circuit, and type some of your work into the forum so it's readable? Thanks.

(you should consider learning to post math using LaTeX -- see the "LaTeX Guide" link below the Edit window)
the circuit:

here is what I did:
(english is not my first language so sorry if i get any terms wrong)
I thought R3, R4 and R5 form a triangle so I turned it into a star for easier calculation and I did the same for R6 R7 and R1.
Then I thought R34 and R35 are parallel so I calculated that too and the same I did for R61 and R71.
Then I thought all of them were connected in order meaning I could add them all together.
That is:
R3435 +R45 + R67 + R6171.
I got the answer 2, I need to get 3.
Where did I go wrong?

How could we possibly know where you went wrong when you have not shown your work ???

SHOW EVERY STEP

phinds said:
How could we possibly know where you went wrong when you have not shown your work ???

SHOW EVERY STEP
It's at the beginning of the thread

Edy56 said:
It's at the beginning of the thread
Yes, and it got this response:
berkeman said:
It's pretty hard for me to read your uploaded pictures. Can you post a better picture of the original circuit, and type some of your work into the forum so it's readable? Thanks.

Edy56 said:
the circuit:
View attachment 321978
here is what I did:
(english is not my first language so sorry if i get any terms wrong)
I thought R3, R4 and R5 form a triangle so I turned it into a star for easier calculation and I did the same for R6 R7 and R1.
Then I thought R34 and R35 are parallel so I calculated that too and the same I did for R61 and R71.
Then I thought all of them were connected in order meaning I could add them all together.
That is:
R3435 +R45 + R67 + R6171.
I got the answer 2, I need to get 3.
Where did I go wrong?
That's what I did here?

Edy56 said:
That's what I did here?
No, you listed the steps you did not show any of the calculations.

THIS:
"I thought R3, R4 and R5 form a triangle so I turned it into a star for easier calculation and I did the same for R6 R7 and R1."

is a set of steps. It is not calculations.

phinds said:
No, you listed the steps you did not show any of the calculations.

THIS:
"I thought R3, R4 and R5 form a triangle so I turned it into a star for easier calculation and I did the same for R6 R7 and R1."

is a set of steps. It is not calculations.
I am not sure as to how write that. I can draw it, but I don't know how to write those steps.

If you mean calculating new Rs it's just basic multiplication and I have in the picture.

I'm sure you could figure out how to type numbers and equations, but I can see that it would be a lot of work. Perhaps someone else here will be willing to look at your hand-written work and follow it to see if they can find your error.

phinds said:
I'm sure you could figure out how to type numbers and equations, but I can see that it would be a lot of work. Perhaps someone else here will be willing to look at your hand-written work and follow it to see if they can find your error.
Okay

I cannot read the component values.

You do not need the Y to Δ transform.
Current source Ig is infinite resistance, so remove it from the circuit.
Voltage sources, E1 and E2 are zero resistance, so short them.
R1 = R5 = R6 = 2k;
R3 = R4 = 1k;
R7 = 4k.
Series; +
Parallel; //
R16 = R1 + R6 =
R34 = R3 + R4 =
R167 = R16 // R7 =
R345 = R34 // R5 =
R2 = R167 + R345 = 3k.

Baluncore said:
You do not need the Y to Δ transform.
Current source Ig is infinite resistance, so remove it from the circuit.
Voltage sources, E1 and E2 are zero resistance, so short them.
R1 = R5 = R6 = 2k;
R3 = R4 = 1k;
R7 = 4k.
Series; +
Parallel; //
R16 = R1 + R6 =
R34 = R3 + R4 =
R167 = R16 // R7 =
R345 = R34 // R5 =
R2 = R167 + R345 = 3k.
I am not sure I understand...
The way I do it, I imagine that power is flowing from a to b and so when it's going from a the power splits in two because of R4 and R5 and thus making them parallel. Why isn't it like that?

Edy56 said:
Why isn't it like that?
Yes, you can do it in the longer way using the inverse Y to Δ transform;
https://en.wikipedia.org/wiki/Y-Δ_transform

Your mistake is that you have the current source, Ig = 0 ohms, as a short circuit, which is wrong. A current source has infinite resistance, which is an open circuit.
You do not need the Y to Δ transform if you make the current source = ∞ ohms.

## 1. What is the purpose of finding the resistance R in a network?

The resistance R in a network is a measure of how much the network impedes the flow of electricity. It is important to know the resistance in order to properly design and analyze electrical circuits.

## 2. How is the resistance R calculated in a network?

The resistance R in a network can be calculated using Ohm's Law, which states that resistance is equal to the voltage divided by the current. It can also be calculated using the formula R = V/I, where V is the voltage and I is the current.

## 3. What factors affect the resistance R in a network?

The resistance R in a network is affected by several factors, including the material of the conductors, the length and cross-sectional area of the conductors, and the temperature of the conductors. Additionally, the presence of resistors or other components in the network can also affect the overall resistance.

## 4. How does the arrangement of components in a network affect the resistance R?

The arrangement of components in a network can affect the overall resistance R in a few ways. For example, connecting resistors in series will increase the overall resistance, while connecting them in parallel will decrease the overall resistance. Additionally, the placement of resistors in relation to other components can also affect the resistance.

## 5. What are some common methods for measuring the resistance R in a network?

There are several methods for measuring the resistance R in a network, including using a multimeter, a Wheatstone bridge, or a digital ohmmeter. Each method has its own advantages and may be more suitable for different types of networks or situations.