Voltmeter readings for this circuit with switches

[karim2360]

TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance)

My thoughts for the first case , one of them must be 12 volt while the other is 0
The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the voltmeter is measurin

 

[Gordianus]

Could you draw the voltmeters?

 

[kuruman]

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• micromass
• Homework students
• Replies: 2
• Forum: Introductory Physics Homework Help

• 

 

[karim2360]

I am not sure I can because i forgot to save this circuit on my device but I will try my best to mark them here

 

[kuruman]

What do you think the voltmeters read when the circuit is as shown in post #4 and why?

 

[karim2360]

What do you think the voltmeters read when the circuit is as shown in post #4 and why?

If key1 was opened and key2 was closed then I think the v1 is zero because no current intensity is flowing in that wire however the current passes in the other wire below where v2 is located because key 2 is closed so it should be 12 volts , that's for the first case

For the second case where both keys are opened , I think that they v1 and v2 should not equal zero as for the fact that both keys are not outside of either voltmeter range , it should read 12 volts just like if we put a voltmeter between two terminals of the battery , I also think both v1 and v2 are equal to zero IF there was a main key to the whole circuit (instead of the two keys we have for both resistors) located outside of both of the voltmeters range like next to the battery or something

 

[Gordianus]

I have another concern- The current sources can't perform whenever any of the switches is open. The circuit makes no sense.

 

[karim2360]

I am not sure I can because i forgot to save this circuit on my device but I will try my best to mark them here View attachment 366541

Edit , the resistance here is 24 Ohm not 1k I apologize for the big confusion

 

[karim2360]

I have another concern- The current sources can't perform whenever any of the switches is open. The circuit makes no sense.

As for the resistance value it was a huge misunderstanding, it should be 24 ohm for each resistance and that's when both keys are closed , I know it's not clear but I would like anyone to address this circuit as a normal closed DC circuit , I promise to do better next time

 

[DaveE]

Sorry to be blunt, but this problem is nonsensical.

There are a few things you should never see in an idealized circuit schematic.
1) A loop that only contains voltage sources. Because KVL says they must sum to zero, which only allows for trivial solutions where they just happen to sum to zero. The KVL/KCL equations are degenerate.
2) A node that only has current sources. Because KCL says they sum to...
3) A series connection of a voltage source and a current source. The voltage source does nothing since the current source will create WHATEVER VOLTAGE IS REQUIRED to make the prescribed current flow.
4) A parallel connection of a voltage source and a current source. The current source does nothing since the voltage source will create WHATEVER CURRENT IS REQUIRED to make the prescribed voltage potential.
5) A current source in series with an open circuit. There lie infinities that will smite your understanding.
6) A voltage source with a short circuit. Because... exercise left to the reader.

note 5) and 6) are really a direct consequence of 1) and 2)

Your instructor is.. wait, I need to be polite here... not doing his best work. Can you find another? Move on, this problem is stupid.

Also, sorry, I didn't actually try to answer your question. I think the voltage at the current source node is undefined. The voltage across is current source is determined by the voltage drops in the rest of the circuit, which, in this case is a conundrum [re. note 2) above].

 

[DaveE]

BTW, in the language of schematics, this smells like AI generated. I've never known a human EE that would create this. As Pauli is reputed to have said 'It's not even wrong'.

 

[kuruman]

I have another concern- The current sources can't perform whenever any of the switches is open. The circuit makes no sense.

I don't think these are current sources. Most likely they are ammeters. With both keys switches closed, the battery provides current (not 1 A) which splits equally at the node. This makes sense.

 

[DaveE]

I don't think these are current sources. Most likely they are ammeters. With both keys switches closed, the battery provides 1 A which splits equally at the node. This makes sense.

Yes, that makes sense. It's not standard nomenclature, but the alternative is ridiculous. But then they shouldn't have values attached. It's not 1A if the switches are open.
https://www.kandh.com.tw/uploadfiles/592/images/Poster/electrical-schematic-symbols.pdf

 

[kuruman]

Yes, that makes sense. It's not standard nomenclature, but the alternative is ridiculous. But then they shouldn't have values attached. It's not 1A if the switches are open.
https://www.kandh.com.tw/uploadfiles/592/images/Poster/electrical-schematic-symbols.pdf

Since we are in the guessing realm, I imagine that this could have started as a multiple answer problem, without the voltmeters, asking the question, What combination of open/closed switches would match the current read by the ammeters (mark all that apply)?

1. Both open
2. Both closed
3. Only top closed
4. Only bottom closed

 

[karim2360]

I don't think these are current sources. Most likely they are ammeters. With both keys switches closed, the battery provides current (not 1 A) which splits equally at the node. This makes sense.

I know right ? I thought something was wrong with this damn circuit and no it it's not AI generated surprisingly , but I think the idea of the whole question here was to know the voltmeter readings on both resistors when you have a closed circuit that contains ( a battery , 2 resistors parallel to each other , both keys next to each resistor ) when both keys are open and when either of them is closed , which one will read Vb (the battery) and which of them will read 0 in both cases

 

[karim2360]

Sorry to be blunt, but this problem is nonsensical.

There are a few things you should never see in an idealized circuit schematic.
1) A loop that only contains voltage sources. Because KVL says they must sum to zero, which only allows for trivial solutions where they just happen to sum to zero. The KVL/KCL equations are degenerate.
2) A node that only has current sources. Because KCL says they sum to...
3) A series connection of a voltage source and a current source. The voltage source does nothing since the current source will create WHATEVER VOLTAGE IS REQUIRED to make the prescribed current flow.
4) A parallel connection of a voltage source and a current source. The current source does nothing since the voltage source will create WHATEVER CURRENT IS REQUIRED to make the prescribed voltage potential.
5) A current source in series with an open circuit. There lie infinities that will smite your understanding.
6) A voltage source with a short circuit. Because... exercise left to the reader.

note 5) and 6) are really a direct consequence of 1) and 2)

Your instructor is.. wait, I need to be polite here... not doing his best work. Can you find another? Move on, this problem is stupid.

Also, sorry, I didn't actually try to answer your question. I think the voltage at the current source node is undefined. The voltage across is current source is determined by the voltage drops in the rest of the circuit, which, in this case is a conundrum [re. note 2) above

Sorry to be blunt, but this problem is nonsensical.

There are a few things you should never see in an idealized circuit schematic.
1) A loop that only contains voltage sources. Because KVL says they must sum to zero, which only allows for trivial solutions where they just happen to sum to zero. The KVL/KCL equations are degenerate.
2) A node that only has current sources. Because KCL says they sum to...
3) A series connection of a voltage source and a current source. The voltage source does nothing since the current source will create WHATEVER VOLTAGE IS REQUIRED to make the prescribed current flow.
4) A parallel connection of a voltage source and a current source. The current source does nothing since the voltage source will create WHATEVER CURRENT IS REQUIRED to make the prescribed voltage potential.
5) A current source in series with an open circuit. There lie infinities that will smite your understanding.
6) A voltage source with a short circuit. Because... exercise left to the reader.

note 5) and 6) are really a direct consequence of 1) and 2)

Your instructor is.. wait, I need to be polite here... not doing his best work. Can you find another? Move on, this problem is stupid.

Also, sorry, I didn't actually try to answer your question. I think the voltage at the current source node is undefined. The voltage across is current source is determined by the voltage drops in the rest of the circuit, which, in this case is a conundrum [re. note 2) above].

You didn't have to be polite XD , I was really confused too but I tried to solve this question in every way possible haha

 

[karim2360]

Since we are in the guessing realm, I imagine that this could have started as a multiple answer problem, without the voltmeters, asking the question, What combination of open/closed switches would match the current read by the ammeters (mark all that apply)?

1. Both open
2. Both closed
3. Only top closed
4. Only bottom closed

That would have made ALOT of sense

 

[kuruman]

That would have made ALOT of sense

I concur with @DaveE. This problem is badly formulated and has nothing to teach you that you don't already know. Time to move on.