I’m in the same boat, but I can still repair a 1976 electromechanical pinball machine. Sometimes I’ll get stuck and I’ll solicit advice online (pinside.com is a wonderful resource). I always have to preface my question with “assume I don’t have a multimeter”. I mean, I do; I just don’t know how to use it and I just can’t seem to learn.
This gives me another idea for a question: What causes the loud crack of thunder when lightning strikes?
Counter with: “If my ancestors came from Ireland, why are there still people living in Ireland?”
I never understand why this is so hard to figure out. All monkeys did not evolve into humans…one primate species out of many that were extant millions of years ago ultimately became the ancestor of all humans. The others either died out or evolved into another species (or more likely, many other species)—maybe even into another species of monkey.
Similarly, just because your ancestors immigrated to the U.S. from Ireland doesn’t mean that every person in Ireland left. In fact, most stayed behind, and they left descendants who are still living in Ireland.
In the case of evolution, I think the disconnect is this erroneous belief that evolution has an ultimate purpose, and that it is the destiny of all monkeys to evolve into humans. This of course is not remotely the case, any more than all people living in Ireland are destined to someday emigrate to America.
The air surrounding the lightning bolt is rapidly heated and explosively expands, creating thunder. The same thing happens with a spark on a dry day…just on a much smaller scale.
Oh cute! So the little click you hear is baby thunder.
Exactly. Baby thunder.
To understand AC, get a 12 V battery, some wires, and a 12 V incandescent light bulb. Hook up the wires between the battery and light bulb. The bulb lights. Now reverse the polarity of the battery. The bulb lights. Reverse the polarity every two seconds. The bulb will flash on and off, of course, due to the “dead” time during switching; it’s basically a square wave, with abrupt changes in the polarity of the voltage. But that is essentially AC.
There are the differences between this experiment and powering a 120 VAC incandescent light bulb in your house, though. For one thing, the voltage waveform isn’t a square wave like with the battery experiment described above. The voltage smoothly increases, peaks, goes down to zero, reverses, increases, peaks, goes down to zero, reverses, etc. etc. etc. Smoothly and continuously. And instead of saying the voltage “reverses,” we can instead say the voltage goes from negative, to positive, to negative, to positive, etc. etc. Also, the voltage peaks at around 170 V; it smoothly goes from 0 V, to +170 V, to 0 V, -170 V, to 0 V, to +170 V, to 0 V, to -170 V, etc. etc. Finally, the switch in polarity happens quickly, at every 0.0083 seconds.
So the hot vs. neutral thing… go back to the battery experiment. Note that everything is isolated from the earth (earth = the actual dirt). Now take one of the wires between the battery and light bulb (it doesn’t matter which one), and connect another wire between it and the dirt. Now continue reversing the battery polarity every two seconds. Note that, regardless of what the battery is doing, one wire is always electrically connected to the dirt, while the other is not. The one that is electrically connected to the dirt is called the “neutral,” and the other is called the “hot.” Hope this helps.
Finally, it is unfortunate it is called alternating current (AC). It should have been called alternating voltage (AV). Oh well.
This whole paragraph is completely unclear. In the third sentence of the quoted paragraph above, what is “ it” referring to? (i.e. in the phrase “…between it and the dirt.”).
Assuming “it” means one of the two original wires, why would you want to do this? And why isn’t this done with the original DC circuit? And why doesn’t grounding one of the two wires not short out the circuit to ground when the higher voltage side of the battery is connected to that wire every two seconds?
Yea, sorry about that. “it” is one of the two wires. In other words, pick one of the wires, and then add a third wire that connects this wire to the earth.
For the battery & light bulb? It’s not necessary. I mean, you can if you want. But it won’t matter. I was simply demonstrating what we do for the AC power that enters your house.
Again, put a battery and incandescent light bulb on a plastic table. Connect the battery to the light bulb using two wires. Now pick one of the wires, and then electrically connect this wire to the dirt using a third wire. We now call the wire you picked the neutral, and the other wire hot. This is a DC circuit, of course. Now grab the battery and reverse its polarity as fast as you can. Now it is (sorta) AC. Neutral wire is still the neutral wire, and the hot wire is still the hot wire.
With the battery example, the third wire (that connects one of the wires to the dirt) is not even needed. It’s not doing anything. This is simply to illustrate what we do for the AC power that enters your house. For your house, that third wire (between one of the wires and the dirt) is important. Because without it, both wires could “float up” to thousands of volts relative to the dirt. (Why? Because unlike the battery example, the wires are fed from a non-ideal transformer with a primary winding that is at 7200 V relative to the dirt.) To keep everything from floating up to a super high voltage, we connect one of the wires to the dirt. This “nails them down,” so to speak. (Oh, and it’s really not two wires going to your house. It is three wires. But same deal, and I won’t get into that.)
What’s the difference between analog and digital?
Yes, I know the textbook definition. But by digital i don’t mean binary, it could be ternary, or 4 logic states, or billion. So is an analog world just “complicated digital” with hideously large but unique truth table? On the other hand, “digital” isn’t some magic or green characters Matrix-style going through a circuitboard. Down to a microscope, pardon, oscilloscope level every “0” and “1” is not just a square wave, it’s an imperfect analog spike with some noise.
So in our everyday use, analog and digital make sense, but seen through wider lenses it gets not only blurry, but an existential dread if you let it.
I really should know this one! 