Homework help : The difference between these 2 circuits

In summary, the document explains the key differences between two types of electrical circuits: series circuits and parallel circuits. Series circuits have components connected end-to-end, resulting in a single pathway for current, where the failure of one component affects the entire circuit. In contrast, parallel circuits have multiple pathways for current to flow, allowing components to operate independently; thus, if one component fails, the others remain functional. The summary highlights the implications of these configurations on current flow, voltage distribution, and overall reliability.
  • #1
Maghraby
8
1
Homework Statement
Electrophysics
Relevant Equations
the source voltage
I want to know the difference between the two circuits below , and Why don't I bundle both batteries into one 24V battery?
pls help me in this .

Screenshot_20231124-142953_EveryCircuit.png


This is the original circuit:

Screenshot_20231124-151612_Notein.png


And to merge the two batteries , What is the resulting value of a battery resulting from the merger?
I thought that the value would be 24 volts, but after experimenting on the application, I found that it must be 12 volts, how is that?

Screenshot_20231124-152037_Notein.png
 
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  • #2
Maghraby said:
Homework Statement: Electrophysics
Relevant Equations: the source voltage

I want to know the difference between the two circuits below , and Why don't I bundle both batteries into one 24V battery?
pls help me in this ,,
View attachment 336082
Hello @Maghraby ,

:welcome:

Please read the PF guidelines : we need you to post your attempt at solution before we are allowed to help.

In the mean time you could redraw the circuits in such a way that it becomes clearer ...

##\ ##
 
  • #3
BvU said:
Hello @Maghraby ,

:welcome:

Please read the PF guidelines : we need you to post your attempt at solution before we are allowed to help.

In the mean time you could redraw the circuits in such a way that it becomes clearer ...

##\ ##
done !
 
  • #4
I agree with the 12 V.
So: is there a difference between the two circuits, or are they completely identical ?

##\ ##
 
  • #5
BvU said:
I agree with the 12 V.
So: is there a difference between the two circuits, or are they completely identical ?

##\ ##
OK , there isn't difference ,but I want to know why 12 V and not 24 V ?
 
  • #6
Maghraby said:
OK , there isn't difference ,but I want to know why 12 V and not 24 V ?
So, they are different (12 vs 24) but they are not different? Seriously?
 
  • #7
phinds said:
So, they are different (12 vs 24) but they are not different? Seriously?
You misunderstood. I mean the difference between the two circuits in the first picture.When I merge the 2 batteries , Why will the battery after merging be divided into 12 volts and not 24 volts?
 
  • #8
Imagine that you are an electron traveling around that circuit. When you get to the junction between the two batteries you have a choice about which battery you go through. This is fundamentally different than a circuit with one battery.

Can you show us a schematic with two 12V batteries that is equivalent to one 24V battery?
Can you show us a schematic with two 2Ω resistors that is equivalent to one 4Ω resistor?
Can you show us a schematic with two 2Ω resistors that is equivalent to one 1Ω resistor?
 
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  • #9
I claim there IS a difference between the two circuits. I redraw them first:

1700835680902.png
1700835708990.png
D and D' are both at 0 V thanks to the fact that both voltages are the same.
So effectively both voltage sources are in parallel, hence the 12 V and not 24 V.

That's no longer the case if one of the two voltages changes.
As an example you could recalculate the first circuit when the voltage on the right is 24 V.

##\ ##
 
  • #10
BvU said:
both voltage sources are in parallel
Nope. There's some resistors in the way.
 
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  • #11
BvU said:
I claim there IS a difference between the two circuits. I redraw them first:

D and D' are both at 0 V thanks to the fact that both voltages are the same.
So effectively both voltage sources are in parallel, hence the 12 V and not 24 V.

That's no longer the case if one of the two voltages changes.
As an example you could recalculate the first circuit when the voltage on the right is 24 V.

BvU said:
I claim there IS a difference between the two circuits. I redraw them first:

D and D' are both at 0 V thanks to the fact that both voltages are the same.
So effectively both voltage sources are in parallel, hence the 12 V and not 24 V.

That's no longer the case if one of the two voltages changes.
As an example you could recalculate the first circuit when the voltage on the right is 24 V.

##\ ##
OK , thanks for your help !
 
  • #12
BvU said:
So effectively both voltage sources are in parallel, hence the 12 V and not 24 V.
I understand that you covered yourself by saying "effectively", but that is VERY misleading since they are NOT in parallel and telling a beginner that they are is not a good idea, Due to circuit symmetry, they ACT as though they were in parallel which, clearly, is what you meant by "effectively" but again ... it's misleading to a newbie to circuit analysis who likely doesn't understand serial vs parallel.

@Maghraby, I'd like to see you answer the questions in post #8.
 
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  • #13
phinds said:
I understand that you covered yourself by saying "effectively", but that is VERY misleading since they are NOT in parallel and telling a beginner that they are is not a good idea, Due to circuit symmetry, they ACT as though they were in parallel which, clearly, is what you meant by "effectively" but again ... it's misleading to a newbie to circuit analysis who likely doesn't understand serial vs parallel.

@Maghraby, I'd like to see you answer the questions in post #8.
I barely understood the problem previously and I considered that the two batteries were connected in parallel as mentioned previously, so if you have any other clarification, please clarify. I am sorry if there is any spelling error. My primary language is Arabic and I try as much as possible to write in English.
 
  • #14
phinds said:
I understand that you covered yourself by saying "effectively", but that is VERY misleading since they are NOT in parallel and telling a beginner that they are is not a good idea, Due to circuit symmetry, they ACT as though they were in parallel which, clearly, is what you meant by "effectively" but again ... it's misleading to a newbie to circuit analysis who likely doesn't understand serial vs parallel.

@Maghraby, I'd like to see you answer the questions in post #8.
My answer for the question in post #8 is :

Yes, I can display a schematic with two resistors of 2 ohms, which is equivalent to 4 ohms by connecting them in series, and it can also be equal to 1 ohm by connecting them in parallel.
 
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  • #15
Maghraby said:
I barely understood the problem previously and I considered that the two batteries were connected in parallel as mentioned previously, so if you have any other clarification, please clarify. I am sorry if there is any spelling error. My primary language is Arabic and I try as much as possible to write in English.
The voltage sources are NOT in parallel and BvU's having said that they were was a mistake, which he admits. They happen to ACT as though they were in parallel, in the sense of not doubling to 24V in a final circuit, but they are not actually in parallel. He did not mean to mislead you, but he did. If you do not understand this, then you need to review the basic definition of series and parallel until you understand WHY they are not in parallel.
 
  • #16
phinds said:
The voltage sources are NOT in parallel and BvU's having said that they were was a mistake, which he admits. They happen to ACT as though they were in parallel, in the sense of not doubling to 24V in a final circuit, but they are not actually in parallel. He did not mean to mislead you, but he did. If you do not understand this, then you need to review the basic definition of series and parallel until you understand WHY they are not in parallel.
Well, thanks for your help.
 
  • #17
Maghraby said:
What is the resulting value of a battery resulting from the merger?
I thought that the value would be 24 volts,
Nobody, except maybe @DaveE, seems to have addressed your key error, the belief that voltages in parallel add. They don't. Voltages in series add.
Equal voltages in parallel double the current, but the voltage is the same as for each individual battery.
Unequal voltages in parallel gets more complicated as you would have to consider internal resistance to avoid infinite currents.
 
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FAQ: Homework help : The difference between these 2 circuits

What are the main differences between series and parallel circuits?

In a series circuit, components are connected end-to-end, so the same current flows through each component. In a parallel circuit, components are connected across common points or junctions, providing multiple paths for the current. This means the voltage across each component in a parallel circuit is the same, while the current can vary.

How does the total resistance differ in series and parallel circuits?

In a series circuit, the total resistance is the sum of the individual resistances. In a parallel circuit, the total resistance is less than the smallest individual resistance and is calculated using the reciprocal formula: 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn.

How does the failure of one component affect series and parallel circuits?

In a series circuit, if one component fails, the entire circuit is broken and current stops flowing. In a parallel circuit, if one component fails, the other components can still operate because they have separate paths for the current.

What happens to the current and voltage in series and parallel circuits?

In a series circuit, the current is the same through all components, but the voltage is divided among them. In a parallel circuit, the voltage is the same across all components, but the current is divided according to the resistance of each path.

Which type of circuit is more efficient for household wiring, series or parallel?

Parallel circuits are more efficient for household wiring because they ensure that each appliance or device receives the same voltage. Additionally, if one device fails, it does not affect the operation of others, providing reliability and safety.

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