How to find equivalent resistance of this circuit?

In summary: I believe that you've misunderstood the problem. In summary, this conversation is about a homework problem that is asking for the addition of two 10 ohm resistors to produce a series equivalent resistance of 20 ohms. The problem asks for the last resistor in the circuit to be combined with the sum of the two resistors to produce the series equivalent resistance. The problem is difficult to understand, and the conversation is about a problem that is not the original homework problem.
  • #1
nfcfox
36
0

Homework Statement


http://imgur.com/vUoRrhO
upload_2016-4-14_23-54-20.png
[Note: Image copy inserted by moderator]

Homework Equations


Req for parallel is 1/Req=1/R+1/R...

The Attempt at a Solution


I have never seen a circuit like this and I'm not sure as to how I would go about calculating it since there is a resistor inside of the parallel section. All those resistors are 10 ohms.
 
Last edited by a moderator:
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  • #2
nfcfox said:

Homework Statement


http://imgur.com/vUoRrhO

Homework Equations


Req for parallel is 1/Req=1/R+1/R...

The Attempt at a Solution


I have never seen a circuit like this and I'm not sure as to how I would go about calculating it since there is a resistor inside of the parallel section. All those resistors are 10 ohms.
Combine the two series resistors first (what is the equation for combining series resistors?), and then combine the two resulting parallel resistors. :smile:
 
  • #3
berkeman said:
Combine the two series resistors first (what is the equation for combining series resistors?), and then combine the two resulting parallel resistors. :smile:
Isn't there only one series resistor? I'm still not sure how to do this...
 
  • #4
Two resistors are in series if all the current that passes through one also passes through the second.
 
  • #5
NascentOxygen said:
Two resistors are in series if all the current that passes through one also passes through the second.
Ok ok I see now. So the resistor on top is added with the one on the right or left then that is put in parallel with the other one... Still kind of weird though because after adding those 2 resistors, wouldn't it not be in parallel after that?
 
  • #6
nfcfox said:
So the resistor on top is added with the one on the right or left
Right or left? Which one is in series with the resistor on top?
 
  • #7
The current enters and leaves this circuit via the terminals on the left.

After adding two resistances the resultant may be in parallel with a third. Perform this simplification in steps, so you don't get confused.
 
  • #8
Here's a picture that might help with the discussion:
upload_2016-4-15_11-15-51.png

Edit: Added resistor identification labels (red).
 
Last edited:
  • #9
cnh1995 said:
Right or left? Which one is in series with the resistor on top?
I think the right.
 
  • #10
Was this question meant to test knowledge of resistor colour coding (which I am long unfamiliar with - does it still exist?), the actual calculation being assumed trivial?:oldbiggrin:
 
  • #11
nfcfox said:
I think the right.
Yes. So what do you get for the answer? Please show your work. :smile:
 
  • #12
berkeman said:
Yes. So what do you get for the answer? Please show your work. :smile:
I already have the answer I found it... I'm just confused as to why adding the 2 10 resistors would then put that in parallel with the last one.
 
  • #13
epenguin said:
Was this question meant to test knowledge of resistor colour coding (which I am long unfamiliar with - does it still exist?), the actual calculation being assumed trivial?:oldbiggrin:
No this is just something I made on a gizmo. It's part of a problem I am doing.
 
  • #14
nfcfox said:
I'm just confused as to why adding the 2 10 resistors would then put that in parallel with the last one.
Adding the two 10 ohm resistors will give series equivalent resistance Req of them. How are Req and the remaining 10 ohm resistor connected?
 
  • #15
nfcfox said:
I already have the answer I found it... I'm just confused as to why adding the 2 10 resistors would then put that in parallel with the last one.
I've added unique identifying labels to the resistors in the figure in post #8. Can you tell us which two resistors you added together and which is the "last one" that you combined with the sum?
 
  • #16
Add the series (top and right) use ohms law to get whatever value that you are missing (I'm assuming that you have one of the other values probably the applied voltage). Then use ohms law to solve for the last resistor on the left. This is a series-parrallel circuit and is easiest to solve when broken down into two separate equations.
 
  • #17
gneill said:
I've added unique identifying labels to the resistors in the figure in post #8. Can you tell us which two resistors you added together and which is the "last one" that you combined with the sum?
R3 and R2 as series then that with R1 as parallel.
 
  • #18
justaman0000 said:
Add the series (top and right) use ohms law to get whatever value that you are missing (I'm assuming that you have one of the other values probably the applied voltage). Then use ohms law to solve for the last resistor on the left. This is a series-parrallel circuit and is easiest to solve when broken down into two separate equations.
I believe that you've misunderstood the problem. It is an entry level problem with three resistors, all 10 Ω. The goal is to reduce the given network to a single equivalent resistance value. It requires the concepts of recognizing series and parallel pairs of resistances and combining said pairs into single values. Eventually a single value representing the entire network's equivalent resistance is achieved.
 
  • #19
nfcfox said:
R3 and R2 as series then that with R1 as parallel.
Correct.
 
  • #20
My bad, I wasn't aware that I couldn't provide a complete algebraic solution. My post was deleted, I really need to read the rules. Add the two in series, that leaves you with two resistors that you can use the equation for parallel resistors to find the total resistance. Good luck
 

Related to How to find equivalent resistance of this circuit?

1. How do I calculate the equivalent resistance of a series circuit?

To calculate the equivalent resistance of a series circuit, simply add up the individual resistances of each component. This is because in a series circuit, the current is the same throughout, so the total resistance is equal to the sum of the individual resistances.

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/R3 + ..., where R1, R2, R3, etc. are the individual resistances of each component. This is because in a parallel circuit, the voltage is the same across each component, so the total resistance is equal to the reciprocal of the sum of the reciprocals of the individual resistances.

3. How do I find the equivalent resistance of a complex circuit?

To find the equivalent resistance of a complex circuit, you can use a combination of series and parallel circuit rules. Start by simplifying any series or parallel sections of the circuit, and then use the simplified values to calculate the equivalent resistance of the entire circuit. Alternatively, you can use the Kirchhoff's laws to solve for the equivalent resistance.

4. Can I use Ohm's law to find the equivalent resistance of a circuit?

No, Ohm's law only applies to simple circuits with one resistor. To find the equivalent resistance of a complex circuit, you need to use a combination of circuit rules and equations.

5. What is the significance of finding the equivalent resistance of a circuit?

Finding the equivalent resistance of a circuit is important because it allows us to simplify complex circuits into a single equivalent resistor, making it easier to analyze and understand the behavior of the circuit. It also helps in determining the total power and current in the circuit.

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