Ungrounded Conductors From Same Circuit on Same Breaker?

[charlie b]

If we lay out two black wires and two white wires and join the two ends of each color to a receptacle while joining the other ends to the breaker and the neutral bar respectively, then we have created parallel wiring (clearly?).

Agreed.

Now if somewhere between the panel and the terminal outlet, we nick off some insulation on one black and one white wire and connect another receptacle, do we not still have a parallel wiring situation?

We do not. The black wire that had its insulation ?nicked off? and connected to another receptacle will no longer be in parallel with the black wire that was not connected to that second receptacle. Some of the current leaving the breaker on the one wire will join up with current leaving the breaker on the other wire. But some current will not, since the nicked wire will pass some of its current through the second receptacle. If 100% of the current flowing on one wire does not join up with 100% of the current flowing in the second wire, then the two wires are not in parallel.

Why is this so controversial?

Because people continue to confuse the concept of ?parallel paths for current flow? with the concept of ?parallel components.? These two concepts are not the same.

Are you are saying that the first situation I describe is parallel wiring, but the second is not?

Yes.

 

[charlie b]

Current only flows in two types of paths, series or parallel.

That is not true. There are circuits that are neither parallel nor series. Here?s a classic example: Take four resistors of various values, and connect them to form a square. Make another square with four more resistors. Now, while holding one square above the other, connect four more resistors, each one going from a corner of the bottom square to a corner of the top square. You just built a cube. Finally, connect one wire to any corner of the cube, and a second wire to its diagonally opposite corner, and apply a voltage source. Current will flow in all twelve of the resistors. But you cannot resolve the cube into a single resistor by combining series or parallel components. Not one of the twelve resistors in the cube is in series with any other, nor is any in parallel with any other.

 

[ggunn]

That is not true. There are circuits that are neither parallel nor series. Here’s a classic example: Take four resistors of various values, and connect them to form a square. Make another square with four more resistors. Now, while holding one square above the other, connect four more resistors, each one going from a corner of the bottom square to a corner of the top square. You just built a cube. Finally, connect one wire to any corner of the cube, and a second wire to its diagonally opposite corner, and apply a voltage source. Current will flow in all twelve of the resistors. But you cannot resolve the cube into a single resistor by combining series or parallel components. Not one of the twelve resistors in the cube is in series with any other, nor is any in parallel with any other.

I disagree. It is complex but deterministic; it's just a voltage divider network. It can be resolved into a single resistance and the current in each resistor can be calculated. It looks like a problem my DC Circuits prof would have come up with to give his students heartburn.

 

[handy10]

Agreed.
We do not. The black wire that had its insulation ?nicked off? and connected to another receptacle will no longer be in parallel with the black wire that was not connected to that second receptacle. Some of the current leaving the breaker on the one wire will join up with current leaving the breaker on the other wire. But some current will not, since the nicked wire will pass some of its current through the second receptacle. If 100% of the current flowing on one wire does not join up with 100% of the current flowing in the second wire, then the two wires are not in parallel.
Because people continue to confuse the concept of ?parallel paths for current flow? with the concept of ?parallel components.? These two concepts are not the same.
Yes.

Very clear explanation. Thanks

 

[charlie b]

I disagree. It is complex but deterministic; it's just a voltage divider network. It can be resolved into a single resistance and the current in each resistor can be calculated. It looks like a problem my DC Circuits prof would have come up with to give his students heartburn.

I presume you are disagreeing with this statement:

But you cannot resolve the cube into a single resistor by combining series or parallel components.

So let's be clear. I know this cube can be resolved into an equivalent resistor. I know it can be done using voltage dividers, or loop currents, or other analytical methods that involve matrix algebra. My statement was that you cannot resolve this into a single resistor by using the following method:
? Step 1: Noting that resistors 5 and 8 are in parallel with each other, combine them into an equivalent resistor.
? Step 2: Noting that that combination is in series with resistor 3, combine them into an equivalent resistor.
? Continue with similar steps, until you are left with only one equivalent resistor.

I was taking issue with the statement that all circuits are either series or parallel. They are not. Here is my key point:

Not one of the twelve resistors in the cube is in series with any other, nor is any in parallel with any other.

 

[ggunn]

I presume you are disagreeing with this statement:So let's be clear. I know this cube can be resolved into an equivalent resistor. I know it can be done using voltage dividers, or loop currents, or other analytical methods that involve matrix algebra. My statement was that you cannot resolve this into a single resistor by using the following method:
? Step 1: Noting that resistors 5 and 8 are in parallel with each other, combine them into an equivalent resistor.
? Step 2: Noting that that combination is in series with resistor 3, combine them into an equivalent resistor.
? Continue with similar steps, until you are left with only one equivalent resistor.

I was taking issue with the statement that all circuits are either series or parallel. They are not. Here is my key point:

All circuits are series and/or parallel. Better?

 

[charlie b]

All circuits are series and/or parallel. Better?

Not better, as it is not true. A circuit can be not parallel, and at the same time it can be not series. The cube is an example. No two resistors (out of the twelve) are in series with each other. No two resistors are in parallel with each other.

 

[Lockandtaged]

From my point of veiw both sides have valid points. What is the danger of this "ring circut"? Was the homeowner a seiral remodler, or did the electrican pull it back to the panel on accidently then say it was on purpose?

 

[John120/240]

From my point of veiw both sides have valid points. What is the danger of this "ring circut"? Was the homeowner a seiral remodler, or did the electrican pull it back to the panel on accidently then say it was on purpose?

No real danger that I can see. The installer was a telephone wireman. It just

seems a waste of time & material IMO.

 

[kwired]

Not better, as it is not true. A circuit can be not parallel, and at the same time it can be not series. The cube is an example. No two resistors (out of the twelve) are in series with each other. No two resistors are in parallel with each other.

A circuit is always a series and sometimes has parallel components.

 

[kwired]

Here is "the cube". Each resistor has a definite series or parallel relationship to other resistors.

Originally Posted by charlie b .. No two resistors (out of the twelve) are in series with each other. No two resistors are in parallel with each other.

I see some that are in series with each other and some that are in parallel with each other, what point are you trying to make:?



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[ggunn]

A circuit is always a series and sometimes has parallel components.

This starts to veer off into the philosophical. I would submit that every circuit has both series and parallel characteristics. Some are mostly series and some are mostly parallel, and charlie's cube circuit is somewhere in the middle. IMO, it's not neither, it's both. Philosophically, that's sort of the same thing, though.

 

[kwired]

This starts to veer off into the philosophical. I would submit that every circuit has both series and parallel characteristics. Some are mostly series and some are mostly parallel, and charlie's cube circuit is somewhere in the middle. IMO, it's not neither, it's both. Philosophically, that's sort of the same thing, though.

Can you draw a circuit that does not have a series component in it? You can have a circuit without a parallel component.

If there is not at least one series component how can you have a circuit? The power supply could be the only series component in a circuit.

The series component could be a parallel connection but as a whole is a series component. Put two batteries in parallel as a power supply. The batteries are parallel to each other but the power supply is in series with the rest of the circuit.

 

[charlie b]

We are getting off track here. Let me remind everyone that the reason I am pushing the point of what is, and what is not, a parallel set of conductors, is that some have claimed the OP?s description represents a violation of the rules regarding parallel conductors (i.e., wires too small). Whether or not there is a violation present, I submit that that is not the violation, based on the fact (and I continue to call it a fact) that no two wires are in parallel with each other. I will try to explain my views in the next post.

 

[charlie b]

Here is "the cube". Each resistor has a definite series or parallel relationship to other resistors. I see some that are in series with each other and some that are in parallel with each other, what point are you trying to make?

My point is that you are seeing it wrong, and whoever published that image has it wrong as well. Back to basics:

Two components are in series if, and only if, 100% of the current that flows through the first component will also flow through the second component. If after leaving the first component, current has a choice of paths to follow, one being the second component, and the other being a third component, then components 1 and 2 are not in series. Looking at the image in post # 91, there is a statement that ?1 is in series with 4 and 12.? That much is true, in that 100% of the current flowing through 1 will flow through either 4 or 12. But please note that 1 is not in series with 4, because after leaving 1, current can flow through 4 or through 12. Since current has two or more paths to follow, after leaving 1, we must conclude that 1 is not in series with any single other resistor. Looking at the entire cube, we must also conclude that no single resistor is in series with any other single resistor.

Two components are in parallel if, and only if, they are connected to each other at both ends, such that 100% of the current entering the pair and splitting between the two components will recombine at the other end. The image in post # 91 states that 1, 2, and 11 are in parallel. That is wrong. They sort of look ?parallelish,? and if they were cars I might say they are parallel parked. But let us not let conversational English get in the way of technical accuracy. You must note that 1, 2, and 11 are connected to each other on their left sides only, not on their right sides. I will say this more explicitly: The right side of 1 is not directly and electrically connected to the right side of 2. Instead, the right sides of 1 and 2 are connected to other components. The current that started at L1, and split and went into 1, 2, and 11, did not rejoin at the other side of 1, 2, and 11. So 1, 2, and 11 are not in parallel. Looking at the entire cube, we must also conclude that no single resistor is in parallel with any other single resistor.

 

[charlie b]

Can you draw a circuit that does not have a series component in it?

Yes. See the image in post# 91. But to make sure I am being clear, that is an image in which no single component is in series with any other single component.

 

[kwired]

We are getting off track here. Let me remind everyone that the reason I am pushing the point of what is, and what is not, a parallel set of conductors, is that some have claimed the OP’s description represents a violation of the rules regarding parallel conductors (i.e., wires too small). Whether or not there is a violation present, I submit that that is not the violation, based on the fact (and I continue to call it a fact) that no two wires are in parallel with each other. I will try to explain my views in the next post.

Attach two conductors together at opposing ends and they are in parallel to each other. They may be different size or length making the resistance of each part different from the other but does not change the fact that they are parallel to each other. The 'ring circuit' is no different. Each parallel portion of the conductors does vary in length size or some other characteristic but is still parallel to the other portion. Two resistors of different value connected to a voltage source are in parallel to each other. This does not mean they both carry the same level of current.

I drew the picture you say is wrong. What is wrong with it. It is what you described is is not? Two resistors parallel to each other make up a parallel component. Three resistors in parallel make up a parallel component. Throw another parallel componet in series and the first is still parallel

You need to know current and voltage in each of these components to caluclate current and voltage in other sections of the drawing don't you.

If I gave you a supply voltage and a resistance value for each resistor you can calculate voltage and current through every point in that circuit.

 

[charlie b]

I drew the picture you say is wrong. What is wrong with it. It is what you described is is not?

There is nothing wrong with the image. It represents a cube, the very example of not-series and not-parallel that I have been talking about. I should have thanked you for supplying the image. The part I called wrong is the statement that some of the resistors are in parallel with each other.

Two resistors parallel to each other make up a parallel component. Three resistors in parallel make up a parallel component.

You'll get no argument from me on this point.

Throw another parallel componet in series and the first is still parallel

I don't understand what you are trying to say with this statement, because you are talking about putting a parallel component in series. I would need to ask you to rephrase this, before I can comment on it.

 

[charlie b]

Let me belabor this point a bit further.

If two resistors are in series, then you can disconnect them from the circuit and replace them with a single resistor whose value is calculated by adding the values of the original two. After having done so, the total equivalent resistance of the entire circuit will remain the same. Look at the image in post # 91, and consider resistors 1 and 4. Imagine disconnecting them both, and trying to replace them with a single resistor. How would you connect that replacement? When you disconnect the two, you will have left #12 dangling in the breeze. If you tried to connect the replacement in series with #12, then you will have changed the total equivalent resistance of the entire circuit. Therefore, we conclude that 1 and 4 are not in series.

If two resistors are in parallel, then you can disconnect them from the circuit and replace them with a single resistor whose value is calculated using a slightly more complex formula. After having done so, the total equivalent resistance of the entire circuit will remain the same. Look at the image in post # 91, and consider resistors 1 and 2. Imagine disconnecting them both, and trying to replace them with a single resistor. How would you connect that replacement? Do you connect it to the 4/12 point, or to the 3/9 point? No matter how you try to connect the replacement, you will have changed the total equivalent resistance of the entire circuit. Therefore, we conclude that 1 and 2 are not in parallel.

 

[charlie b]

The 'ring circuit' is no different. Each parallel portion of the conductors does vary in length size or some other characteristic but is still parallel to the other portion.

The ring circuit is very different. But please keep in mind that my discussions have all been restricted to looking at a single component (including a wire), and looking at its relationship to one other component at a time.

Pick any wire within the ring. I mean the wire that goes from the breaker to the first outlet, or the wire that goes from the fourth outlet to the fifth outlet, or any other wire. Look at that wire and that wire only, and let's call it "Wire X." Now look at the wire that is connected to its left hand side ("connected" by virtue of both being terminated at the same outlet device), and call it "Wire Y." Ask yourself if "Wire X" and "Wire Y" are also connected at their right hand sides. No matter which two wires you pick, the answer will be no. I know that there is a path from the right side of X to the right side of Y. But that path involves other wires, each having some resistance value. I am talking about the left sides of X and Y being attached to a common terminal point, and the right sides of X and Y being attached to another common terminal point. No two wires have that direct connection on both sides. Therefore, no two wires along the ring are in parallel with each other.

Q.E.D.