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

  1. The load controlled by the switch determines what size circuit breaker is required, as well as the size of the wire.
    1
  2. The demonstration with the battery is inappropriate, so don't worry about it. DC circuits don't really have a "neutral" and a "hot" or "live" wire is any conductor that is not grounded. The battery diagram was an attempt to relate the simplicity of a simple battery & lamp circuit to that of a home circuit.
    1
  3. It's the same as how a motor works, just the opposite. In a motor, a electromagnet creates a magnetic field which acts on a fixed magnet to generate rotational force. In a generator, a rotating magnetic field acts on a conductor to produce electricity.
    1
  4. I'm not a bonafide expert, but that sounds like how I'd do it in your situation.
    1
  5. He said it in the vein as "1100" is "eleven-hundred".
    1
  6. Yes, electrician messed up. The code was changed in 2011 to prevent this exact scenario. You will have to find a smart switch that does not require a neutral.
    1
  7. GFCIs/RCDs don't care about the ground wire. All they do is monitor how much current is flowing through both the regular wires. Because electricity always flows in a closed loop called a circuit, the current in both wires should be the same. If the wires don't have the same amount of current, then current is leaking (returning through a different path) somewhere, and the GFCI/RCD trips. If the ground wire has potential, then hopefully it is enough to cause a short circuit and cause the over-current device to trip. If the GFCI is faulty, then you have other issues.
    1
  8. Think of a hose filled with water. If you push more water into one end of the hose, the force will carry across all of the water until the other end of those, when some water will be pushed out. Most of us connect empty hoses which fill with water as they're used, but electrons are in everything, so an electrical conductor is always "full". The electrons don't necessarily physically "knock" each other. Remember that electrons are not a discrete particle around the nucleus but instead a "cloud" of where the electron could be. Also remember that like charges repel, so two electrons wouldn't have to touch to repel each other. It is that force of "repelling" which actually is all the work.
    1
  9. "Basic" means in terms that lay people can understand. It does not mean knowledge everyone does understand. This video contains a very basic explanation of how electrons around an atom work without a thorough lecture and understanding on quantum mechanics. It's enough to explain the basic idea in a manner people can relate to without muddying up with mundane details. That's what "basic" means.
    1
  10. A "hot" wire is any conductor that is not grounded. But, yes, the term is usually limited to AC circuits in North America. The term "neutral" shown with the battery is not appropriate; I think the video author was just trying to relate home circuit wiring to the simplicity of a battery and a lamp.
    1
  11. The nail is made out of iron, which is naturally magnetic. When the nail is inside the magnetic field, the field and iron atoms exert force on one another, and the weaker one moves.
    1
  12. Yes. Just make sure that the circuit and outlet amperage is equal to or greater than what the welder is rated to draw.
    1
  13. So do you understand what AC is now, or not? If you do, then you should know why the concept of polarity with AC is meaningless.
    1
  14. It should be obvious the switch has only two terminals. If this is confusing, then they should leave into someone qualified and knowledgeable. This stuff isn't rocket science, so if it doesn't click pretty quickly, best leave it to others.
    1
  15. KaibabaCorp HQ The white wire is now required to be a neutral in the switch box per Code. This is to ensure future-proofing, as more and more "Smart" devices are being installed in walls to replace traditional switches. Those Smart devices need their own power, which requires a neutral connection (just like the light bulb does). The second demo in this video is now illegal in new installations, but is still perfectly safe and works fine, unless you need to install a Smart switch. The first demo in this video has the neutral in the box with the switch, so there is no problem there.
    1
  16. They're not. Think of it as they just don't travel as far.
    1
  17. What do you want to know about contractors/relays? (A contractor is jut a relay.) A relay is simply a switch controlled by another circuit.
    1
  18. If you want the outlet to be on all the time, then you can only "tap in" where the power from the panel comes to the first switch, and there must be a neutral in that box. If you want the outlet to be switched by the three-way switches, then you can only "tap in" after the final switch, and there must be a neutral in that box.
    1
  19. A "hot wire" is any conductor which is not grounded. Most automobiles have (–) grounded systems, but (+) ground systems also exist. It doesn't really matter which is employed, as long as it's consistent. In direct current (DC) systems, polarity matters. Electrons are negatively charged, so they are drawn to positive charge because opposite charges attract. Electrons "flow" (–) to (+). Electrocution is death by electric shock. A car battery is not likely to electrocute anyone, at least not without significant effort. You cannot get shocked if you don't complete a circuit. A circuit is a complete path from the power source back to the source.
    1
  20. The idea is to use a single 3-conductor cable, to keep costs down and simplicity up. A three-way switch inherently requires three hot wires, so using 3-conductor cable works out. Marking the white wire as hot is an "exception" that lets this cost-effective practice work. Newer codes forbid this practice in most instances. You either need to run an additional cable to handle the switched load, or install less common 4-conductor cable to ensure a neutral wire is present.
    1
  21. It sounds like a switch that can be used as a "two way" switch (like in this video) or a three-way switch. A neutral is required, so that smart switch would only work in the first or third scenarios shown in the video here.
    1
  22. Knob & Tube wiring having a ground is news to me!
    1
  23. You can be electrocuted with a tiny voltage and current applied directly to the heart. Electrocution is death by electric shock, but more specifically, it is an electric shock which disrupts your heart's ability to conduct the signals that cause it to beat. Those signals are weak to begin with, so it doesn't take much to overwhelm them... but your body is a big wet complex blob of flesh, and current flow through the body is a complex thing. It comes down to luck and physics, but the higher the voltage, the easier it is for current to overcome the resistance of your body.
    1
  24. Examine the wires and the terminals on the switches. Many devices will let you do this just by taking the cover plate off the switches. Usually the "Common" terminal is darker than the others. If you can see that, you should be able to see what colors the wires are going to each terminal. If you see some whites connected, then you have Option 2 or 3 listed here. In that case, you'll need to shut the power off, and remove the unscrew the switches from the boxes, and inspect the cables going in and out of the boxes to figure out which is which.
    1
  25. 5:46 Err, it's the Greek letter Mu, which is the symbol for "micro-"
    1
  26. Don't take it too literally. It was, in my opinion, a poorly-conceived example meant to parallel the simplicity of a DC circuit with a common battery and light with that of a AC house circuit with a light.
    1
  27.  @Air-buds  You probably want to wire the fan's hot wire to the hot wire entering the box from the panel. It will also go out to the switch. Once it comes back from the switch, that wire can be connected to the "light" hot wire (which is often blue, but check the instructions). This wiring will cause the fan to be controlled only from the pull chain, and the light controlled from the switch.
    1
  28. Because it's connected to the neutral terminal on the transformer, which, ideally carries no current.
    1
  29. Options 2 and 3 no longer meet code for locations where the Code requires neutrals in every switch box (with a few exceptions). The options shown in the video are perfectly safe, have been used for decades, and are more economical, but the Code changes are for future-proofing with smart devices which require power to operate. As a general rule, every switch box must have a neutral conductor in it, even if it's not initially used. This means Options 2 and 3 would either have to have a separate cable ran beyond the second three-way switch and back to the light, or a 4-conductor cable installed.
    1
  30. Winding the opposite direction would have the same effect as reversing the polarity.
    1
  31. The neutral wire is grounded, so there is very little voltage potential between neutral and ground (or neutral and a grounded casing).
    1
  32. Science does not prove things to begin with, so your argument is moot.
    1
  33. I'm no pro, but if I understand your question, then any listed lighting device for 120VAC should be fine. The most common listing agency in the U.S. is Underwriter's Laboratories (UL), but there are others.
    1
  34. Cutting the white wire is worse.
    1
  35. Grounding: The act of connecting to a ground system (whether earth ground or frame ground); the conductor dedicated to this connection. Grounded: Sharing the same electrical potential (voltage) as the ground (earth or frame); a conductor which has been connected to ground. Earth: The act of connecting something to the soil so as to share the same electrical potential as the Earth; the conductor dedicated to this connection; most fixed grounding systems are earthed. Bonding: The act of electrically connecting two things to ensure they are at the same electrical potential. Neutral: A conductor which, in ideal conditions, carries no current at the source; the conductor which represents a balance between two or more other electrical potentials; is usually Grounded—the groundED conductor.
    1
  36. They are all aspects of the same thing. A 9 volt battery has a potential difference of 9 volts across its terminals. If you take two 9V batteries, the negative terminals are both 9V and so would have zero potential difference between them. Voltage is the difference between electric charges or electrical potentials. Using the water analogy, voltage is the similar to the pressure of the water inside a hose. If you connect two hoses to a valve and pressurize the water in the hoses on each side of the valve to the same amount, there is zero pressure on the valve. If you open the valve, no water will flow. Electromotive force is the force of nature acting to convey an electric charge. It refers to the force itself, such as the plunger being pushed into a hose to increase pressure on the water in the hose, or the force of the pressurized water on the closed valve in the previous example. The force is measured in volts. If there is no voltage, there is no electromotive force.
    1
  37. A short-circuit is a circuit path of little resistance from the source and back to the source. Because there is no resistance to the flow of current, as much current can flow as the source can produce. This can quickly increase the circuit's wires beyond their current capacity, causing them to melt or catch fire, and can also permanently damage the source. Because a short circuit's low resistance causes a lot of current to try to flow very quickly, it's the easiest condition for an overcurrent device such as a circuit breaker (or MCB) or fuse to detect.
    1
  38. Yes. Grounding one of the conductors is done mostly for safety, as it removes the electrical casual potential for that conductor. In theory, a person could stand on the ground and touch the grounded conductor and not get shocked. (In practice, there can be eddy currents between the earth and the grounded conductor, depending on how the grounding is accomplished, so it would not be wise to do this.) DC current sources can be grounded, too. Sometimes the Earth itself is used as one of the conductors in a circuit, and this is not uncommon with high-voltage DC transmission line systems.
    1
  39. Yup!
    1
  40. It's a photo finish!!
    1
  41. Electrons are negatively charged, so how could (+) indicate a concentration of them?
    1
  42. Yes. The fan is generally wired directly to the incoming hot so that it's controlled by its pull chain only. The hot also goes to the switch and back and is wired to the light only so that the light can be switched from the wall.
    1
  43. I was hoping he'd use the Long scale. :D
    1
  44. The terminals on the switch don't matter. I think it's more logical to have the black wire be the always hot, and the white-marked-black wire be the switched hot.
    1
  45.  @kurtrowland5587  Oops. Not a typo (which is a simple mispelling). I just didn't read what I wrote before posting it. :) Corrected.
    1
  46. Aren't those illegal?
    1
  47. You could, sure. Or even any other "hot" color (e.g. red, blue, etc.). The problem is that most of the wiring in a residence is done with non-metallic-sheathed cable. You can't get cable with an extra "black" wire in it. You can get cable with an additional red wire in it. But, both solutions are more expensive, so they were avoided. Current codes would require three-conductor (black, red, white, with ground) cable to be ran to that last switch so there is a neutral in the box, however; the "light first" wiring method shown in the video is not legal for new installations.
    1
  48. It kind-of depends on context. First, let's clarify: a "Hot" wire is any conductor which is not grounded. The neutral is connected to the grounding system, so it is not "hot." A neutral wire in a branch circuit is carries the same current as the hot does. But, at the transformer, the neutral carries no current in ideal circumstances.
    1
  49. They're not the same. The neutral is still grounded. From a physics standpoint, the further away the neutral gets from its connection in the service disconnect to the grounding system, the "less grounded" it is... but it's still grounded. Other than that the neutral is grounded, the two conductors are the same. They are not always interchangeable, though, because of safety considerations. Consider a table lamp. It will have a plug with "hot" and "neutral" and no ground. Because the neutral is grounded, there is not very much voltage potential there if you touch it. If the shell of the lamp socket becomes "hot" then it becomes a safety hazard when screwing in or out a bulb with the power onm because it's easy to touch while energized. The polarized plug on the lamp ensures that the shell of the lamp holder is always the neutral, and the hot is down inside the socket.
    1
  50. Because that would be much less efficient. Two phases is just not sufficient. Three is the minimum required to justify the expense of the fancier generator and extra wires.
    1