/sci/ - Science & Math

you do charge your phone and every electronic with dc voltage though. ac gets rectified when it leaves the outlet

>>11355798
Oh, okay. So then why does AC flow through your charger once it steps down to 12 volts or 15 volts or whatever?

>>11355809
Have you tested it? I can't imagine the battery has some sort of small transformer inside.

>>11355809
because AC is what comes out of your wall

>>11355794
Traditionally AC has been used because it is more efficient to transfer power by means of 3 phase AC compared to DC. The block on your charger (the thing that actually plugs into the power outlet) is a regulated transformer that converts a single phase from mains signal into a 5V DC signal. However, as technology progresses it is becoming more viable to transmit power through high voltage DC. Look up HVDC power transmission.

>>11355809
It doesn’t

>>11355820
It doesn’t

AC is like sticky cum from the wall, too sticky
DC is like girl squirt, nice and good even if it might be piss, nice and good

Ac adapters turn cum into piss basically

AC is generated directly through a motor (wich is basically a spinning electric magnet and some coils).
Its easier to trasmit AC over long distances and its easier to convert high voltages to medium and low voltages with AC trasnformers.

Transistor based electronic devices are supplied with DC voltage because PN junctions only work one way, and with a little ingenuity you can do a lot of things from it.

Batteries also can only generate DC voltage.

So its easier to receive in your home AC, but then it needs to be rectified and smoothed by a power converter so you can feed the battery in your phone or other electronics.

>>11356117
Haha lol so random. You are so funny and random anon, haha.

>>11356004
>>11356140
This. /Thread

>T. EE

>>11356151
explain what voltage is without saying potential differences or making references to gravitational potential energy.

>>11356158
Current is the flow of electrons in any conductor, it can measured in Amperes.

For the electrons to flow in the first place, there needs to be an imbalace of electric charge in two distinct points.

Point A has more electrons, Point B has less electrons.

You can then measure the voltage between theses two points.

It's always relative however, thats why we call it potential difference.
You can have three points or more at the same time and make differente measurements:
p1 = 0V
p2 = 5V
p3 = 7V

p1-p2 = 5V
p1-p3 = 7V
p2-p3= 2V

One concept to remember is: You can have voltage without flow of current.

You can't have flow of current without voltage.

>>11356140 here.

>>11355794
You DO charge with DC, it's AC you dont charge with.

>>11356148
Fuck off back to plebbit

>>11356140
Correct.

>>11356151
Based. EE here as well.

>>11356158
I cannot answer your question in one 4chan post.

>>11356180
This is the definition of voltage only for an electrostatic field. The general definition of “voltage” in an EE way is EMF - electromotive force.

>>11355794
>DC voltage
puts electrons into the phone
>discharging battery
doesn't get electrons out of the phone.

So essentially if you charge with DC there will be a buildup of electrons over time. I expect these electrons will brick the phone before they become dangerous to you.

>>11356238
>>11356246
These posts are both mine. I will take on a trip from here on out

>>11356004
This was also my post my jews

>>11356251
This is so wrong.

Electrons are mobile and can move at different rates through different materials. Every material you know already is full of electrons all the time.

When you use DC voltage you're not filling it with electrons, you're just creating an imbalance of electrons from one pole to another inside the battery.

Battery discharged means it's all neutral. Battery charged means there is imbalance between and potential energy to be used from that imbalance.

>>11356251
No

>>11356257
Also no

A battery uses chemical reactions to create electrical energy. It has nothing to do with a charge distribution. The reaction creates an EMF (i.e. a “voltage”) between its terminals which can supply a current. This current depends on the resistance between its terminals.

>>11356246
Yeah, I knew there was something I was forgeting to explain.
I know there are static charges and emf for voltage, for the fields there are electric and magnetic fields, but while coil magnets are generated by electrons moving, there are pemanent magnets that can be made with AC in some materials, but the reason they retain magnet properties has to do with atom orbitals.

I also heard that some things about charge density can also be explained by orbitals and not just number of electrons alone. It still too complex for me to understand and explain, I'm no Physicst or Electrical Engineer, just an Automation Engineering student.

Most of the times even my professors don't convey these differences in concepts with the same name clearly.

>>11356274
Honestly man it’s all too complex to explain fully or simply. I found out pretty early even my physics and EE professors don’t know all this or at least don’t explain it in an easy to understand way. Some of them have even admitted this openly.

>>11355798
Wtf huh?
/thread already. You should save these bombshell for later down. Can't be instantly solving shit.

>>11356266
>pump electrons one way into an object for hours
>don't end up with more electrons than your started with
Tripfags, not even oncd

>>11356317
I agree, there are full books of this stuff and even then not one has the complete picture.

I said early ITT that PN junction only work one way, but boy, dont get me started on reverse polarization and fucking amplifiers that are DC and AC at the same time.

Really too complex and the boomers that teach me are too incompetent and contradicting each other sometimes. I'm from 3rd world country by the way.

>>11356140
Tell me why it is underwater power cables use DC and not AC?

>>11356367
Never studied these before, maybe I said wrong about AC being good on long distances. The thing about engineering is that you need to know how much it costs and how effective and safe something is for the cost.

I don't study high tension more than the basics in my course, so I know the basics abou the infrastructe of the power grid of my country. I know that the distance between the power plant and my city is 1071 KM, and that there are two distinct powerlines, one that is AC and other that is DC. Why?
I have no idea.

>>11356400
I have read that it is superior for long distances. Which contadicts the whole tesla edison thing from years back. Because of the diameter of the cable perhaps?

>>11356337
You must be misunderstood. A battery does not store electrical energy in the form of a charge distribution, because that would make it a capacitor. Yes, there is a net transfer of electrons, but this does not form an electrostatic field. Rather, the energy is stored as chemical energy.

>>11356140
>feed your phone
nom nom my phone is hungry

>>11356140
I thought DC was easier to transmit over long distances, but AC is easier to step down in voltage? Why are DC high voltage lines popping up all over the place then?

>>11356337
>pump electrons one way into an object for hours
But that's false. Batteries always have two leads and electrons come out at the same rate they enter.

>>11356425
Long distance cables have some problems that they generate other than high resistance, I dont know what they are though.

Economically I know AC transformers are cheaper, so you can go from 300Kv to 220V relatively easy.

DC transformers arent even called transformers I think. Completely dofferent technology, and I suspect its more expensive.

Maybe DC has better properties for long distance cables, and supposing converting stations for DC are expensive and it needs to be done end to end (2 stations for 1 set of cables) it's only economically viable for long distances maybe, while on AC you could have more power loss.

It's all about the pros and cons, and the pros and cons aren't universal in the real world, for each project there is some factor that made someone to choose something over other thing. Sometimes it's the the project has the smartest decisions, sometimes it's full of incompetence and dumb decisions.

But I don't know about these, so I can't answer you objectively.

>>11356469
I think you are probably correct and it is the voltage conversion that makes AC better for household transmission. DC has been the superior long distance form all along.

>>11356448
Technology changes, and it was my error saying that AC long distance is cheaper.

Converting up or down is cheap tho.

>>11356140
Why is 3 phase special

Obviously it covers more than 2 phase
But wouldnt 4 phase be better

>>11356367
There is a way to ask that nicely.

It's been a while, but here is as I remember it:

Loses in high voltage AC wires in air or ground are mostly due to resistance of the wire itself. Not the medium around it, because Impedance (summarily name for Capacitance / Inductivity) of air and ground is negligible. Therefore it does not matter all that much if it's AC or DC. Therefore, since the "conversion" between different voltages is considerably easier with AC, that's why it's predominantly used.

However, once you put the wire in water, the impedance starts playing the more important part in calculating loses, up to a point where having a "frequency of 0Hz" as in DC has an impact. Therefore the savings in loses justify considerably more expensive conversion equipment required on either side.

To put this in perspective, you can literally transform 230kV line into 230V line with a piece of coiled wire. Yeah. That's essentially what transformer is.

To do the same, you need an equivalent of Switched-mode power supply, because no, resistance-based Voltage splitter is really not a good solution, thanks to the incredible losses it introduces.

>>11356481
The more coils the put in the same mechanical-electrical energy converting system the more expensive it gets.
Sure, 4 coils, 6, 8, 12, put as many as you like. But then you need 4, 6, 8 or 12 cables for transmission.
For energy country wide energy distribution for industry 3 phase is better than 2 and cheaper than 4 it seems.

Also for 3-phase motors its really easy to control and start them with the star-trigle connections. If you want to put your 3-phase motor in reverse, just switch the plug of 2 of the phases between each other.

>>11356493
>>11356489
>>11356469

TL;DR:
https://www.youtube.com/watch?v=S7C5sSde9e4
https://www.youtube.com/watch?v=DFQG9kuXSxg

>>11356493
So, is the output of 3 phase actually constant?

>>11355794
https://www.youtube.com/watch?v=mQpzwR7wLeo
https://www.youtube.com/watch?v=CUFVSc5ll4s

>>11356504
the output of 3 phase? If you mean the output of a 3 phase generator, no the output is 3-phase AC.

AC voltage is variable by definition, the same means DC voltage is (mostly) constant by definition.

There is a gif in this thread showing the senoidal output of a 3-phase generator.

>>11356518
But when one wave is down the other are both up half the amount the other is down

If you convert to dc how mcuh error is there ffrlm a consyant signal dc ay same voktge???????

>>11356474
>DC has been the superior long distance form all along.
This is wrong. AC power transmission has too many benefits over DC to list at the voltages we use them at. HVDC is more efficient than AC because of losses from the skin effect. Plus modern power electronics make stepping the voltage up after every load much more practical than anything that was available when the infrastructure was being designed and built.