# Trying to get equivalent resistance of a circuit

• AmirWG
In summary, the conversation discusses a problem with finding the equivalent resistance of a circuit. The speaker initially got an answer of 23.7 ohm, but the textbook says the correct answer is 100 ohm. The expert suggests redrawing the circuit to clearly see the components in parallel and series, which helps the speaker identify the correct answer and understand where they went wrong in their steps. It is also mentioned that there is a minimum resistance of 85 ohm due to the 50 and 35-ohm resistors in the circuit.
AmirWG
i had a problem in my textbook asking me to get equivalent resistance of a circuit , i ended up getting 23.7 ohm as my answer but my textbook says that the correct answer is 100 ohm
you can see my attempt here :

i really want to know what went wrong with my steps

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When you are analyzing a circuit, it helps to redraw it so that it is really clear what components are in parallel, and what are in series. In this case, you could redraw it to look like this:

I suggest that you fill in the dashed portions of this diagram with the appropriate resistances and then do your series/parallel calculations.

davenn, AmirWG and DaveE
tnich said:
When you are analyzing a circuit, it helps to redraw it so that it is really clear what components are in parallel, and what are in series. In this case, you could redraw it to look like this:
View attachment 248018
I suggest that you fill in the dashed portions of this diagram with the appropriate resistances and then do your series/parallel calculations.
i can now see why my steps went wrong and i am even able to get the correct answer now , thanks a lot for helping (:

davenn and tnich
One way to see immediately that the answer must be at least 85 is to notice that there is no way around the 50 and 35-ohm resisters. So there is a resistance of 85 to start with.

AmirWG

## 1. How do you calculate equivalent resistance in a series circuit?

In a series circuit, the equivalent resistance can be calculated by simply adding up the individual resistances of each component.

## 2. What is the formula for calculating equivalent resistance in a parallel circuit?

The formula for calculating equivalent resistance in a parallel circuit is 1/Req = 1/R1 + 1/R2 + ... + 1/Rn, where Req is the equivalent resistance and R1, R2, etc. are the individual resistances.

## 3. Can you use Ohm's law to calculate equivalent resistance?

No, Ohm's law (V = IR) is only applicable to individual resistors and cannot be used to calculate equivalent resistance in a circuit.

## 4. Why is it important to know the equivalent resistance of a circuit?

Knowing the equivalent resistance of a circuit is important for determining the overall current and voltage in the circuit. It also helps in selecting the appropriate components for the circuit.

## 5. What factors can affect the equivalent resistance of a circuit?

The equivalent resistance of a circuit can be affected by the number and type of components, their individual resistances, and the way they are connected (in series or parallel).

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