# Confused about a Result (Circuit Analysis)

• rtareen
In summary, the problems are that the circuit diagram does not make it clear how to interpret the polarity of Vout where it is labelled, and that the equivalent resistor calculation was wrong.
rtareen
Homework Statement
Find the output voltage for the the circuit in Figure 4-22. Find the output voltage if a 500k resistor were placed across the output terminals
Relevant Equations
##\sum V = 0, \sum I = 0##
The problems I am referring to are problems 4-10 and 4-11.

There is no solution provided for 4-10, so I want to check my answer here. However, I don't understand the answer to problem 4-11. Shouldn't it also be 24 V since it is in parallel with the 200 k##\Omega## resistor? I am actually confused about resistors in parallel. Is there a chance its not in parallel due to the 50 k##\Omega## resistor on the left?

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rtareen said:
I want to check my answer here
Ambiguous ! You probably mean you want us to check your answer ? What could possibly be wrong with it ?

Re 4.11: your answer is correct. How did you calculate it ?

Hint: replace the 200 k and the 500 k resistors -- that are in parallel -- by a single equivalent resistor and repeat what you did in 4.10 !

##\ ##

berkeman and rtareen
BvU said:
Ambiguous ! You probably mean you want us to check your answer ? What could possibly be wrong with it ?

Re 4.11: your answer is correct. How did you calculate it ?

Hint: replace the 200 k and the 500 k resistors -- that are in parallel -- by a single equivalent resistor and repeat what you did in 4.10 !

Thanks for letting me know. What about 4.10, is it correct?

How might the polarity of the circuit's voltage source effect your results?

It is unfortunate that the circuit diagram does not make it clear how to interpret the polarity of Vout where it is labelled.

gneill said:
How might the polarity of the circuit's voltage source effect your results?

It is unfortunate that the circuit diagram does not make it clear how to interpret the polarity of Vout where it is labelled.
It should not. It does not matter which way the current is flowing.

BvU said:
Ambiguous ! You probably mean you want us to check your answer ? What could possibly be wrong with it ?

Re 4.11: your answer is correct. How did you calculate it ?

Hint: replace the 200 k and the 500 k resistors -- that are in parallel -- by a single equivalent resistor and repeat what you did in 4.10 !

##\ ##
Im having trouble with 4-11. I found the equivalent resistor. I got:

##R_{eq} = \frac{200,000(500,000)}{700,000} = 143,000 \Omega##

Then I went around the circuit again with KVL. I got

##193,000 \Omega I= 30~V \implies I = 1.55 \cdot 10^{-4}~A##

But then ##V_{out} = R_{eq}I = 30V##

1.55 10-4 x 143 10+3 = 30 ?

(Practising PF on a brand new phone )

##\ ##

rtareen
BvU said:
1.55 10-4 x 143 10+3 = 30 ?

(Practising PF on a brand new phone )

##\ ##
Oh no. I was using 193,000. I see now that that was wrong.

rtareen said:
Shouldn't it also be 24 V since it is in parallel with the 200 kΩ resistor?
It's in parallel so that means both resistors have the same voltage across them. It's just that the voltage is no longer 24 V.

rtareen

## 1. What is circuit analysis?

Circuit analysis is the process of studying and understanding the behavior of electrical circuits. It involves applying mathematical and theoretical principles to determine the voltage, current, and power at different points in a circuit.

## 2. Why am I confused about my circuit analysis result?

There could be several reasons for confusion in circuit analysis results. It could be due to incorrect assumptions, errors in calculations, or incomplete understanding of circuit components. It is important to review and double-check all steps in the analysis process to identify the source of confusion.

## 3. How can I improve my circuit analysis skills?

To improve your circuit analysis skills, it is important to have a strong understanding of basic electrical principles and mathematical concepts. Practice solving different types of circuits and familiarize yourself with common circuit components. Seeking guidance from experienced professionals or taking a course in circuit analysis can also be helpful.

## 4. What should I do if my circuit analysis results do not match the expected values?

If your circuit analysis results do not match the expected values, it is important to recheck your calculations and assumptions. Make sure all circuit components are connected correctly and that you are using the correct values for resistors, capacitors, and other components. If you are still unable to identify the issue, seek guidance from a mentor or experienced professional.

## 5. Are there any tools or software that can assist with circuit analysis?

Yes, there are various tools and software available that can assist with circuit analysis. These include simulation software, circuit analysis calculators, and online circuit analysis tools. However, it is important to have a solid understanding of circuit analysis principles before relying solely on these tools.

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