Comments by "Jovet" (@jovetj) on "The Engineering Mindset" channel.

  1.  @nikkimalones1324  You are welcome, I am glad I could help.
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  2. This is a very good video! Thank you.
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  3. If there are only two non-green screws on the switch, then 1) turn the power off 2) remove cover from the switch and switch from the wall 3) remove the two wires and use a wire-nut to tie them together. 4) put the switch and cover back together.
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  4. Really helpful video. Nice visualizations! The only thing I don't like is around 1:47 when you're using terminology of "hot" and "neutral" with regards to a battery source. Since you later touch on the difference between AC and DC, and how the center-tapped neutral works, this seems particularly egregious.
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  5. What? Edit: The wires shown running alongside each other are in the same cable bundle or conduit. It's not rocket science.
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  6. The "hot" and "neutral" are not swapping places. Remember that a "hot" or "live" wire is a conductor that is not grounded. The neutral is not only the center-tap out of the transformer, but it also is grounded. Remember that a battery has a static polarity. (+) is always positive, and (–) is always negative. The only way to reverse a circuit is to take the battery out and hook it in backwards. But, that is basically what AC does, 50-60 times a second. At one moment of AC, the "hot" may be (+) and the neutral would be (–). A few milliseconds later, the "hot" would then become (–) and the neutral is (+). And a few milliseconds after that, they switch back. The switch back and forth is not instantaneous. If you graph it out, it is a beautiful sine wave. It is not important to know what the polarity of the circuit is, because it doesn't matter—it's constantly changing. It is only important to know which conductors are grounded. And then, if more than one conductor is not grounded, which is which (e.g. multiple phases).
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  7. You mean at about 2:55? Because it's not a single wire. The first cable comes in from the service panel, and goes to the first switch box and stops. Then a second (3-wire) cable goes from that box to the second switch box, and stops. Then a third cable goes from that switch box to the light. Even if you were not completely changing types of cable, it would be too time consuming to try and split open a cable so you don't cut the white wire. This all assumes you're using nonmetallic sheathed cable, which is the most common in homes. If you were running this circuit a conduit, you then would have precise control over each conductor, and could definitely make just one continuous long white wire. Just make sure you leave a loop or two in each box it passes through, just in case it needs to be tapped into later. Those are wire nuts not "caps."
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  8. I don't know about the UK, but in the U.S. stupid refers to an inability to think clearly or logically, or at all. Knowledge cannot "fix" stupid any more than shoving data into a computer makes the computer smart. That being said, knowing how to think is a learned behavior, and some people never learn. But learning how to think makes you less-stupid.
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  9. Remember all materials resist the flow of electricity. That resistance mostly manifests as heat, which is the answer to your question.
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  10. It depends on the routing of the cables. The usual goal is to save money with the shortest cable runs possible. Having the power feed cable to an extra 20+ feet to get to a switch and back is going to cost extra money and installation time.
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  11. Watch that segment at 8:16 again. It says the breaker might not trip, not that it definitely will.   The point is that current will travel through the earth, but it doesn't travel nearly as easily as through a fancy copper conductor. Enough current could flow through you to stop your heart, but not be enough current to trip a circuit breaker. How much current can flow through the earth depends on many factors, such as the type of soil, the how far apart the ground rods/connections are, the voltage, etc.
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  12. No you're not. The second example is no longer up to code!
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  13.  @jonburhan5478  You now have to run a neutral to the switch box, even if it's not currenetly used. Three-conductor cable is needed. The switch loop is carried on the black and red wires.
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  14.  @jonburhan5478  2011, I believe. 404.2(c).
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  15. Not quite. The travelers can be wired in any way, and then your XOR won't work. The simplicity is the selection of the alternate path to complete the circuit no matter switch switch is used.
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  16.  @robertbrandywine  In essence, there is no difference between the neutral and the hot wires for circuits branching off of the main panel. They are both necessary conductors for a 120V circuit. The only difference between them is the neutral is grounded, and the hot(s) is not. The connections on the transformer, especially the secondary side, are called taps. The neutral is connected to the center tap because it's right in the center of the secondary coil. A 120 volt load is connected to one of the end taps ("hots") and the center tap. This completes a circuit providing 120 volts because we're only using half of the 240 volt secondary coil. (Remember, in a transformer, the number of coils of wire in the coil determines the voltage.) Power flows through the neutral because it is the circuit. It's just as if the rest of the secondary coil isn't there at all—you can pretend it does not exist. A 240V device uses both hots (both end taps) and power flows through both of them because they are both the circuit; the neutral is not used and so no power flows through the neutral for a 240V circuit. The power the neutral actually carries between the transformer and the panel is the imbalance between the load on the two end taps for the sum of all circuits on the panel. Electrically, the two halves of the secondary coil of the transformer are in series to each other. The two halves of the panel are, too; it's just the panel part is a lot more complicated because of all the sub-circuits. I hope you now see that the answer to your last two questions you asked is "yes". Just be sure to avoid phrases like "negative" and "positive" in the AC world.
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  17. The switch is always electrically ahead of the light in the circuit. But it doesn't have to be first as far as the routing of the conductors. The difference is the routing of the conductors, but the circuit architecture is the same.
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  18. Correct. One phase only.
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  19. That's a pretty recent code change, but yes.
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  20. In most residential situations, you are using non-metallic-sheathed "Romex" cable. You don't have a choice of wire colors. NM-2 cable is Black and White; NM-3 is Black, White, Red, BNM-4 is Black, White, Red, Blue (or Black, White w/black stripe, Red, White w/red stripe). You have to use the wire colors you have as efficiently (e.g. cheaply) as possible. When the white wire is NOT acting as a neutral, it's supposed to have the black markings on it at each end. In that situation, it's another hot wire, not a neutral.
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  21. The whole reason for the ground wire, and grounding the washing machine frame to it, is so that should the frame become energized, it is able to follow the ground path back to the neutral in the main panel. That completes a low-resistance circuit, allowing much current to flow, quickly tripping the breaker or blowing the fuse.
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  22. 1) The two "hot" wires shown here are still the same phase. 2) The circuits connected between the two hots are essentially connected in series. The neutral to the transformer only carries current when the neutral-hot load of one hot does not match that of the other. There's still no polarity because alternating current. 2) Current will not flow from the neutral to ground because the ground does not complete a circuit, any more than touching a terminal on a battery (and nothing else) causes current to flow into you. See also: birds on a power line. 3) Because the neutral is connected to the ground wire, they are at the same potential. If properly wired, the only time you could get a shock from any grounded metal surface is when a ground fault is in progress. The purpose of the ground wire is to get a large fault current to flow to cause the over-current device (circuit breaker or MCB) to trip quickly. Thus, the chances of actually getting a shock are low, but possible.
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  23.  @Dedread  It is very simple. Where the white and black wires go to the light fixture in the video, simply splice additional wires to go to all the other lights.
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  24. The neutral is connected to ground which allows one of the circuit conductors to be at ground potential. Then, only the non-grounded "hot" or "live" conductor can shock you. We do not use 2-phase here. It's a single phase, usually described as split-phase. Multi-phase installations are rare in residential wiring but are common for farms and industries and other commercial premises. Some three-phase installations can also have a split-phase segment. Running less voltage around most of the house makes it a safer in case of accidental contact. Most service drops into homes are completed with aluminum wire, not copper. Larger cable is needed for aluminum, but it is still cheaper. Solid (rigid) wire is only used for conductors on utility power circuits sized #10 AWG or smaller. It is slightly smaller and provides clean terminations without extras like ferrules. It is generally not difficult to work with solid wire, but there are times when lots of the thicker stuff can try your patience.
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  25. Canadian electrical service and devices are very similar to those in the United States. For most intents and purposes, they're identical. Some of the wire color codes and rules are slightly different, but not much. Multi-phase service to a single or dual-dwelling residence is very rare in the US and Canada. The only exception usually is a farm where multi-phase motors are employed. Three-phase service is very common to farms, and commercial properties, and bulk-residence buildings such as high-rises and the like. Basic residences have no need for multi-phase service.  Single phase service is almost always completed with three wires (for 120/240 volt availability). Some basic service drops such as for a traffic light may only be 120V. Two or three-phase service can be provided through three or four wires, depending on the specific configuration.
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  26. What do you mean?
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  27. But it's still called the neutral.
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  28. I didn't know black and white colorblindness was a thing.
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  29. AnantaSesaDas - This video is an adequate but very basic explanation about why three-phase power exists and how the phases work. Most homes and some businesses are only supplied with one phase. It doesn't matter which phase is used, but as Joe Meso points out, the power company will want to keep the loads on the phases as balanced as is practical. The distribution of three phase power is more complicated than shown in the video. Usually, the phases are interconnected in some way, creating what's called a "delta" or a "wye" circuit. "Delta" circuits require four wires, and are the most common power line configuration you'll see that are not transmission lines. In these circuits, the voltage potential across the three phases and to the fourth neutral wire is usually not equal. 240/208/240 volt three-phase service is common. Higher voltages are also around, but note that one of the voltages is not the same. Here it matters knowing which phase has a different voltage, so "random" won't work. In the U.S., the wires coming into your home are not phases like this. Instead, one high voltage phase is fed into a transformer which steps down the voltage to 240 volts. But the transformer's output has what's called a "center tap" which means a third wire is connected to the middle of the output winding of the transformer. This means that the original, full winding of the transformer is still 240 volts, but the voltage across the middle wire to either of the other two is 120 volts. This requires three wires into your home. Your grandpa's house does not have 240 volt service at all. In a building with three phase service like described above, there may be secondary transformers in the building to convert the three-phase power to regular 240/120 volt service for lights and regular electrical equipment.
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  30. What happens when you rub a balloon on your hair? It builds up a static charge, and your hair starts to stand up. Lightining is the result of AIR rubbing on the EARTH. The soil is the balloon, and the air molecules are your hair. Once enough charge builds up... ZAP!
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  31. Staircases are a better example. No point in having a light for a staircase that is only operable from just one end of the staircase! It's not just a convenience issue, it's a safety issue. Consider a kitchen, or living or dining room, that has 3 entrances. A switch should be placed at each entrance which can operate the room's light. It's not just a safety issue, it's a convenience.
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  32. Yes.
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  33. Yes, DC current flows negative to positive. The power source creates a "surplus" of electrons at one end of the power source (e.g. a battery). The surplus will "flow" to wherever there's a deficit at which the voltage can overcome the resistance.
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  34. No it is not. The "Hot" and "Neutral" on the battery are misleading and inappropriate, but the current through both wires to and from the light is the same.
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  35. You're right, it doesn't matter, except that the neutral is grounded, and is safer in some situations. A light bulb socket is a great example. An Edison base has the screw shell as one contact and the tip as the other. Normally the tip is "hot" and the screw shell is "neutral." It's easy to touch the screw shell, especially when inserting/removing a bulb, and if this were the "hot" it could be quite a shock. But, since the neutral is grounded, there is little voltage potential to get shocked from.
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  36. Because basic non-metallic cable has two conductors: black and white. They don't make black-black cable, and if they did, it would just be an added expense to keep around for that ONE thing.
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  37. The wires shown running along next to each other are in the same run. They can be in the same cable or the same conduit. Just one switch for that light? Hmmmm
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  38. The first coil was uninsulated because it was one strand of a larger conductor, but it worked fine because the loops of the coil were not allowed to touch one another.
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  39. Your first paragraph is correct. The neutral essentially does double-duty. Because the voltage and polarity are constantly changing in alternating current, AC current is not as much of a demand on a conductor as DC is. The shared neutral can do double duty because both of the two hot wires are out of phase with each other. Neutral versus ground is not too complicated. The first thing to remember is a circuit does NOT need a ground to work. All circuits are a complete loop, or path from the source, through the loop, and back to the source. AC or DC, makes no difference. All a complete loop. More complex circuits will have many branches and diversions, but it's still a bit loop. No complete loop, no current flows anywhere. You can think of it like the blood vessels in your body. They are just a big, complex loop. The major vessels carry a lot of blood, but they branch into smaller and smaller ones, only to come back together into larger ones and go back to your heart—the power source. This means every basic circuit needs only two wires. One going from the source, and one going back to it. Usually the two wires are kept relatively close to one another, for safety and convenience, but they don't HAVE to be. A while back it was realized that it was safer if one of those wires is connected to the Earth. This eliminates the voltage potential between it and the ground, so it can't shock you. It still carries the same current as part of the circuit, however. But no matter what voltage it's at at that moment, the voltage difference is always the same as the ground, since it's connected to it. That means one of the wires is grounded (or earthed), and the other is ungrounded.  It was then realized that metal chassis and other equipment parts could become the same voltage difference as that other ungrounded conductor when they're not supposed to. If that happens, a person could touch those parts and form a new circuit path through his body and back to the ground or grounded conductor. So, it was decided to connect all those metal parts to each other and the Earth too. That way, if any of those parts got energized, the power would be easily taken down to the earth, back through the ground connection to the grounded conductor, and then back to the source. This would likely cause a short circuit (complete path with little resistance), resulting in a rapid overcurrent and a fuse or circuit breaker blowing. The wire that connects all the metal parts that should never carry current together is called the grounding conductor, or ground. The grounding conductor should never carry current except when something is wrong... and then, ideally, only for a brief period.  The neutral is the common conductor in your first paragraph, which is also grounded. The wire actually connecting it to the ground is the ground wire. The neutral is a required part of the circuit because it normally carries current. The ground carries current only when something is wrong, as a safety feature. Additionally, that neutral is only grounded at one spot: the main disconnect after the transformer. This prevents bad current interplay between the neutral and grounding, system which can happen otherwise. Polarized plugs do not provide a ground connection. Since they have only two prongs, there is no ground prong. Remember, I said above that a ground wire is not required... only the two circuit wires are needed. What polarized plugs do do is make some electrical equipment safer, when it's important that the grounded conductor (the neutral) be connected in certain ways. A lamp is a good example. The screw base of a light bulb socket should always be the grounded neutral, never the "hot" wire. Polarized plugs ensure that's the case.
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  40. Because all of the circuit must pass through the resistor, it will always have a cumulative effect on the circuit. So, it does not matter where the resistor is. Think of the water in a hose... you can kink the hose anywhere along its length and the water will stop flowing.
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  41. If you have an unswitched hot, and a neutral and ground, then yes you can stick an outlet there.
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  42. A phase is not the same thing as a circuit in a building.
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  43. Electrical setups are basically the same everywhere. It's just the voltages and specifics of equipment that differ. Switches in any country work exactly this way. Just the wiring colors will be different.
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  44. Not exactly. One reason is because the neutral is grounded, and the "hot" is not. "Neutral" also refers to a particular position in the scheme of the power source. For Y three-phase, it's the conductor common to half of all the phases. For North American split phase, it's the center tap of the one phase transformer. Both the hot and neutral are carrying the same load (depending on the circuit topology and location in the circuit) so are otherwise the same.
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  45. If both switches are controlling the lights, then they must be 3-way switches. Power comes from the fuse or breaker panel, and goes into the special-colored common terminal of the first switch. There the power goes to one of the two traveler wires, which are the other two same-color terminals on the switch. The travelers go to the other switch "in reverse" of the first. The common terminal of the second switch is switched output, which goes to all of the lights. The lights are wired in parallel with each other—the switched hot wire splits to all three hots on the lights.
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  46. I've tried to explain this to my brother multiple ways and he just doesn't get it. Hopefully the visuals of this video will help him!
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  47. If you have black, red, and white wires between the fan and the switch, you can control both from the wall. Take the back wire at the fan going to the switch and connect it to the black wire from the breaker panel. At the switch, feed that black into both the fan and light controls. The output of the fan control can go onto the red wire, and the output of the light control can go onto the white wire marked black. At the fan box, connect the red and white-marked-black wires from the switch to the appropriate hot wires of the fan. Connect the white neutral from the panel to the neutral(s) of the fan/light. Note that there will not be a neutral in the switch box, but it will work with a regular switch. To install a smart device as the switch device, you'll have to install one that does not require a neutral.
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  48. What? The guy wire holds the pole up so it doesn't get pulled over. It doesn't carry current or have any grounding function.
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  49.  @tedlahm5740  Oh, I think I see what you're talking about. A "wire" that holds up other wires in an arial catenary but carries no current itself is called a messenger wire. The reason the neutral does not need insulated is that it's grounded at that point. It's grounded at distribution transformer, and it's grounded at the service panel it's going to.
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  50. Why do you say that? Option 1 is the most straightforward.
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