Electrical Engineering Thread

[Anonymous No.9978789]

In this thread we discuss anything and everything relating to electrical engineering.

Which EE field are you in/getting into/wanna get into?
What do you like/hate about it; what's objectively good/bad about it?
Feel free to tell us more about it, what are you working on, etc.

Which fields pay the most?
Which do you find most interesting?
Which ones are best regarding job security?
Which ones are gonna get more/less relevant (needed) in the future?

What are your thoughts on microwave engineering?
How about power engineering?

Are laser technology, optoelectronics, integrated photonics, nanoelectronics or spintronics worth getting into?

[Anonymous No.9978910]

EE undergrad here. I'm interested in machine learning and my department offers plenty of courses related to it that are MSc level. I have to pass the Signals and Systems II course first though so I'm taking an Introduction to Data Mining class this semester. Already did Algorithms and Data Structures.

I can't say I'm that interested in ICs or power systems. I find the signal processing aspect more interesting. There's this branch of ML called probabilistic machine learning where signal processing plays a huge role so yeah, that's what I want to get into.

[Anonymous No.9978912]

Guessing I might as well repost this.
New to EE and I really interested in radio frequency and microwaves and might do it as a concentration instead of control systems. What are some projects I can do and materials to consume? Any tools I should know how to use or simple projects?

Also heard if you're going to projects with radios I should get a licenses. What level would I need?

[Anonymous No.9978929]

Computer Science grad getting my first dev job

considering going back to school and getting an MS in EE, is this going to make me an hero myself?

[Anonymous No.9978959]

>>9978929
Try learning a bit on your own see if you like it before going committing time and money

[Anonymous No.9978983]

>>9978912
I highly suggest moving over here.

>>>/diy/1452945

It's a very active general for electronics.

[Anonymous No.9979103]

>>9978789
question for EE's

why for the love of god do you use "j" instead of "i"? everybody in physics and math uses i for the imaginary unit

and don't say i is current. I is current. upper case.

[Anonymous No.9979116]

>>9979103
EE undergrad here. I still use the i for the imaginary unit and I for current. I like being contrarian I guess?

[Anonymous No.9979143]

>>9979103
Because people were using i to represent current before imaginary numbers were used for circuits so they just used j so no one gets confused.

[Anonymous No.9979152]

>>9978789
first year electronics major, am I allowed here?

[Anonymous No.9979160]

>>9979152
Hi fellow. I'm third semester right now. Hope you like the field. Pretty cozy tbqh.

[Anonymous No.9979164]

>>9979116
EEs are contrarian using j, especially when you consider that J is for current density. The whole point of not using i was so you didn't confuse it with I.

[Anonymous No.9979166]

Can someone redpill me on what EET is?

[Anonymous No.9979201]

>>9978959
any recommendations? I have an arduino to toy around with and have been looking at a few EE courses on edx. My dev job is going to be working closely with RTC/embedded systems although I wont start on them

[Anonymous No.9979224]

>>9979103
i is used for alternating currents while I is used for the amplitude

[Anonymous No.9979232]

>>9979164
the point of not using i is so you don't confuse it with i=i(t)
>>9979224

[Anonymous No.9979269]

>>9979232
totally lost

i and i(t) are visually not the same.... ?
if you're talking about i meaning a DC current, then i = i(t) = constant (Amperes), then this notation is brainlet level

current generally IS a function of time, and needing two letters to distinguish a constant function from a varying function is pretty dumb imho

[Anonymous No.9979280]

Best topology for a 12V to +/-360V 200mA (max) DC-DC converter? I'd also like a +180V tap as well if possible that can also draw up to 200mA.

All things considered seems like cascading two boost converters probably isn't the best option. I've heavily considered flyback converters but I'm having trouble with the design. Peak primary current is too high, close to 20A. I really need that much lower, my 12V source can't deliver anywhere near that current, plus I don't wanna use fuck huge wires and large terminals. I've also had issues with non-dissapitive snubbers not actually doing any snubbing (and my MOSFETs blowing up) and dissapitive snubbers melting my resistors and diodes. To help mitigate this problem I've tried double ended flyback designs though with that I can't reach my output voltage I want.

Recommendations for transformer cores and switching controller please and optimizations of circuit design please.

I can modify design for +/-180V and use voltage doubler to reach +/-360V if necessary. I just need to ensure drawing large loads on the 180V rail doesn't load down the 360V rail (desu the 360V will have a high impedance load that probably won't draw more than 10mA or so at worst but 180V could draw over 100mA)

[Anonymous No.9979285]

>>9978789
I'm doing computer systems engineering as part of a double degree, it's mostly electrical with like 1 4th year unit swapped out for an algorithms unit. I will have an honours project and a couple of summer internships under my belt before graduation. How less likely am I to be able to get a job than general electrical engineers and has anyone even heard of computer systems engineering?

[Anonymous No.9979300]

>>9979232
And that's fucking gay when the most general form of current is a volume current, denoted J(r, t).

[Anonymous No.9979303]

computer engineering student here, what are good books to teach electrical engineering, I know already calculus I, II and III, and physics. I'm really fond of that career.

[Anonymous No.9979769]

>>9979269
What the fuck are YOU talking about? i and i(t) represent the same thing: current that depends on time (former is just shorter).
You don't want to confuse THAT with imaginary unit i; that's why j is used.

[Anonymous No.9979942]

>>9978912
>consume hydrocarbons for energy

But in all seriousness, EE MSc with focus on RF, microwave and remote sensing here...

My tip is to get a software defined radio unit and read up on cool radioastronomy shit that you can do on a shoestring budget

[Anonymous No.9980133]

>>9978789
Mech.E undergrad. I just failed 3 units in a single semester. My Weighted Average is fucked. will I ever get a job?

[Anonymous No.9980139]

I'm in compE and I either want to do some embedded systems job, or go into software entirely. Engineering is soul crushing.

[Anonymous No.9980191]

>>9979769
i(t) implies that you're speaking about instantaneous current, and therefore that current varies over time, whereas just i doesn't imply anything so it would be bad communication to use 'i' when referring to AC current

[Anonymous No.9980193]

>>9978789

Undergrad here, is robotics a meme? I could take those courses but not too sure if its really worth it later

[Anonymous No.9980220]

>>9980193
That depends on what you want to do later. Also you can always take or sit more lessons, there is nothing wrong to learn more for whatever reason.

[Anonymous No.9980227]

>>9980191
You don't seriously expect me to write your autistic "(t)" everywhere do you? If anything is bad communication, it's cluttering our equations with useless bullshit that carries no information we didn't know already. When I write i, I implicitly mean i(t). You sound like a type of faggot that would write dy(x)/dx instead of simple y'. There is a reason why we use single letters in equations u=Ri and not "voltage = resistance * current". No need to pointlessly increase verbosity by adding (t) to get u(t)=Ri(t).

[Anonymous No.9980275]

>>9980227
There is a need in specific situations, and there are reasons to use dy/dx as opposed to y', especially when dealing with partial derivatives. Mathematicians understand that being precise with your notation is effective and useful.

You're probably either an uneducated dumb shit who doesn't know what they're talking about, or someone who's been in the industry so long that they've forgotten academia exists and that applications outside their specialised field exists. Adding the (t) on the end expresses extra information that could be crucial depending on the situation.

[Anonymous No.9980351]

>>9979103
It is for current though, I is only current using physics notation.

Sedra & Smith is a great example of why EE notation is what it is. Lowercase i with a capital subscript denotes a current that has both constant and time varying components (AC DC mix). Lowercase i with lowercase subscript denotes the purely non-DC part of the current, capital I denotes DC only. The point of doing this is to decompose nonlinear (Semiconductor) circuits into two linear circuits, as usually (but not always) the AC component is also considered to be mathematically 'small' for the purposes of linearisation.

At the same time we'd still need to do Fourier Analysis, so complex numbers are unavoidable, hence, j.

[Anonymous No.9980371]

>>9979280
Kinda hard to say without knowing more specs of your 12V source, how much sustained/peak current it can really handle and what kind of loading characteristic it has. That should really dictate what topologies are even viable, as the one example you've given is clearly limited by that.

Also, mosfets blowing up from a bad snubber? what kind of diode are you using here? are they as physically close to the FET as possible? There's usually only two ways FETs die in a situation like this, either they're not switching on and off fast enough or the snub circuit is too slow. How were they being driven?

[Anonymous No.9980968]

>>9980133
I know a guy who got a job by lying that he did Bachelors degree (he got a three year technical degree in reality). So, you can always lie if desperate. Or pursue internship or masters.

My average is fucked as well btw

[Anonymous No.9980969]

>>9980371
I'm too lazy to finish the full schematic right now but this should give you a general idea of what I wanna do. T2 is a current sense transformer since current sense resistor probably drop too much power. Opto-isolator based voltage feedback from the +180V rail. All other is unregulated. Voltage source is lead acid battery 12V though I'd like the option to also be able to power it from a 12V wall brick if possible.

I've think driving the deflection plates doesn't require high current so I don't need lots of current on the +/-360V rail. I do need 100-200mA on the +180V rail though so the converter should do like 40W.

My FETs blew up on older designs because the LCD snubber circuits didn't actually do anything about the inductive spike when the FET switched off and it exceeded the FETs voltage rating. RCD snubbers worked better but using values that were low enough to kill the spike resulted in the diodes and resistors getting really hot. I tried regular diodes, schottky diodes, and TVS diodes but to no avail.

[Anonymous No.9981008]

>>9980969
I mean, the secondary looks alright. I'm a little curious about the driving side of the primary tho, the gate driver looks a little weird to me, stacked NPNs and not a complimentary pair? How does the gate discharge? Why not just let the 3843 handle the gate directly?

Do you even need two FETs for this, and if so why not the complimentary pair? You don't really have a charge pump to overdrive the gate so I'd be cautions about M2 not being driven linear reliably and popping because of that.

[Anonymous No.9981015]

>>9981008
>>9980969
Me again. Unless you were just throwing the schem together quickly and couldn't be assed to find the matching PNP, this gate driver has a lot of problems, look at the 20W dissipation.

[Anonymous No.9981016]

>>9981008
Low side and half-bridge MOSFET drivers apparently use two NPN or N-channel MOSFETs rather than complimentary pairs. I'm not sure what the reasoning is but I'd guess it's probably because NPN/N-channel devices are generally faster. You want a gate driver because MOSFETs have a high gate capacitence and as such will have a time constant which will limit how fast you can turn them on and off. Gate drivers are basically current sources that can source sink high current to rapidly charge and discharge them. While I could use a gate resistor or let it discharge internally via 3843 this is probably a better way.

The two IRFZ44s in that configuration is a doubled ended flyback and the main advantage of it is reducing the voltage stress across the transistor to the maximum DC input voltage (I forgot the diodes in the schematic) Seems to make sense for me to use this. I don't mind buying an extra transistor.

[Anonymous No.9981017]

>>9980351
>I is only current using physics notation
J(r, t)

[Anonymous No.9981018]

>>9981015
You don't drive it from 12VDC though. It's driven off the PWM output from the 3843.

[Anonymous No.9981022]

>>9979166
EET is just the more vocational version of EE. This means you will not go above Calc 2, your science courses will be general physics most likely and you will be doing more simple versions of core EE courses. What you take in Electric Machines or Circuits is different in content from the EE version of those classes. People have strong opinions on the matter and I have no dog in that race. Some say EET's are just bargain bin fake engineers with easier classes, while EET's will say that the standard EE curriculum is all theoretical autism that is utterly pointless unless you plan on grad school.

From my viewpoint and that of some others that evaluate these programs, the EET program is closer to what engineering was 100 years ago compared to today. You will be less informed on higher level EE math and physics, but you'll also leave school with a better idea of how to do shit from the get go. If you want to go to work straight away and have the salesmanship to sell your degree as equally valid as EE, you might enjoy EET. If you want the traditional prestige and rep EE gets with the additional autism of a primarily theory-based education, then do the standard engineering degree and just tough it up.

I'm a retard that dropped out, had looked into EE and EET when I had the time and energy. Went to a CC and was considering doing a 2-years EET degree, decided to instead opt for an IT 2-year degree and just get life started. At 22 I don't have the luxury of making the right choice. Be fucking sure of what you do before committing, re-routing is a bitch after blowing thousands on your education.

[Anonymous No.9981023]

>>9981017
If you really want to be a pedant, I is used for filimentary and average (time or space) current, K is surface current density, and J is volumetric current density. Current Density is not the same as current tho, so I wasn't wrong.

[Anonymous No.9981030]

>>9981018
>>9981015
nvm, I see even with the pwm at 50% duty cycle the power dissipation is still a problem. I'd preferred to use something like an MC34152 but orCAD didn't have a model for it.

[Anonymous No.9981032]

>>9981023
You just pointed out why the argument for j over i as the complex unit is retarded. Sure, you can define line, surface, and volume currents using I, K, and J respectively, but they could just as easily be denoted J_l, J_s, and J, or just shortened to J if context was obvious (like how I is technically a vector, but is almost always written as a scalar). It's retarded to buck convention that everyone else follows. EEs patently have it intuitively wrong writing their wave equations with exp(jwt) instead of exp(-iwt) to add insult to injury.

[Anonymous No.9981035]

>>9981030
Yeah the DC was just to show what it would be doing on the high side of the PWM, until you get that sorted out you can't really say that the FETs are doing what you expect them to. I notice the text you attached doesn't show how the gates are being driven, it's probably assuming some sort of charge pump front end to drive the gates at ~2VCC. I'm not saying the two FET design is bad, just that I'm not convinced it's going to behave properly as it is in this schematic

[Anonymous No.9981051]

Hi EEs, can you tell me about photon current and how electrons get caught up in energy transmission.

[Anonymous No.9981062]

>>9981035
Fuck it. I'm just gonna use a complimentary NPN PNP pair. It's probably not gonna make a huge difference at 100kHz switching frequency and if it does I'll just drop the frequency until it doesn't. It does seem to drastically drop the power dissipation. If I have issues with that I'll get some dedicated gate driver ICs.

[Anonymous No.9981074]

>>9981032
If you're trying to say that using j and J for current going forward is the more consistent thing to do then I wouldn't exactly argue with you much, except for justification I gave here: >>9980351
throwing around more subscripts is going to clash with how signal components are indicated in electronic circuit analysis. It really comes down to, probably, a couple hundred years of current being denoted with I, and the inertia behind continuing its use. From that perspective, switching the imaginary unit to j is just a pragmatic fix, really.

I don't really know why one would consider exp(jwt) less intuitive than exp(-iwt) - no criticism but have just never genuinely sat down with a person who uses the other convention to hear their take on it.

[Anonymous No.9981119]

>>9981051
Gonna need you to elaborate on that if you can

[Anonymous No.9981213]

>>9979166
EET programs are for technicians. They are a lot more practical than theoretical and act as a common background for technicians so they can learn on-the-job quickly. The programs tend to differ at each institution by what the nearby industries request. The place I'm at in Alberta features a lot of instrumentation stuff due to all of the oil companies around here. I am in a 2 year program and have 7 classes per semester, none of which are arts or filler. In terms of math, the highest you will learn are partial differential equations.

[Anonymous No.9981335]

So I'm just getting into an electronics hobby, and I would like to build a 300 volt capacitor bank out of salvaged camera flash capacitors, and I wanted to build a charging circuit instead of using the one in the cameras. So if I made a flyback converter using a mosfet like the IRF540 driven by a NE555 oscillator in astable mode to a ferrite EI transformer with 10 turns primary and 300 turns secondary, and ran it with 10 volts, and put the output through a UF4007 with a capacitor for smoothing, would it work?

pic unrelated

[Anonymous No.9981428]

>>9981035
Alright, I've made some changes including changing the MOSFET drive circuitry to a complimentary NPN-PNP pair and have added in all the other components for feedback and timing. I'm also pleased to see my power estimates were likely way off and it seems I can get my 200mA with only 15W, which with this core and turns ratio only corresponds to about 5.4A peak primary current according to the shitty calculator I made in labview which is a lot better than 19A so I'll take it. I think this'll work... hopefully.

[Anonymous No.9981482]

>>9981428
I did make a minor error where I put the effective permeability in instead of the inductance factor into my calculator. The B65813 actually have an Al of 630nH not 225 which is it's effective permeability. I changed the core to the B65811 instead which has an Al of 250 which is as close as I could get. This will change the turns ratio to 7:28:28.

[Anonymous No.9981512]

>>9979942
Not the anon you're replying to, but you do have any specific recommended SDR units or sites for a noob to get started?

[Anonymous No.9981899]

>>9981119
A generator spins magnets, the magnetic field is energy, photons, the ambient heat of the surroundings. The energy enters the conductor atom. Atoms do have temperature correct?? The energy transfer is photonic in nature, valance electrons are carried along for the ride too.

[Anonymous No.9982198]

I'm getting started with a basic course in electronics, and it was surprising to learn that most EEs don't fully understand what makes circuits work. The explanation from my textbook said it's like a long chain of atoms where electrons continually repel each other forward from the negative end of the power source at the speed of light, but I've also read that the electrons aren't exactly moving much at all, and that the real energy travels on the outside of a wire in a kind of field. I assume at least one of those statements sounds retarded, and it's not necessary to know this yet, but I am curious. Is there a way to explain it to an undergrad? If so, I'd appreciate it if someone were to explain it.

[Anonymous No.9982248]

>>9982198
Most give up because of the mishmash of classical and quantum explanations used to justify their observations and models. Which is fine to an extent, as classical modeling does a good enough job most of the time.

For starters, it's true that electrons don't move very fast at all. Look up drift velocity of electrons in metal and semiconductors, it's nowhere near the speed of light. However, like a Newtons cradle, the motion of one electron influences the motion of adjacent electrons. This action is what propagates along a conductor at the speed of light; it's the propagation of a voltage wave, not a 'wave of electrons' per se. By analogy to the newtons cradle again, because the balls are touching the impact travels along as a pressure wave, at the speed of sound in metal, even though none of the balls are moving that fast. The speed of light is so fast though, that turning on a light switch seems instantaneous, so we just neglect the time it takes for the waves to travel unless we're operating at frequencies/time scales where it becomes significant, like RF circuits.

Now that's a quantum, err, maybe just particle view of current in an electric circuit: electrons or ions moving and influencing each other. The classical view is that current is a kind of ideal fluid of positive electric charge, which is a useful and accurate approximation in a majority of cases.

Lastly, it's also true that energy actually does travel along the outside or surface of a conductor, especially when the current is alternating at a high frequency. Once you have a decent idea of the explanations and distinctions I gave above, go look up the Skin Depth of Conductors to understand why the energy distributes the way that it does. For bonus points, see if you can find a quantum/ particle justification for the Skin Depth too.

[Anonymous No.9982503]

Remember, do not take the power stream.

[Anonymous No.9982560]

>>9982503
because its boring or hard to get a good salary job?

[Anonymous No.9983696]

>>9982560
Basically boring. All I have ever done in past 10 years are to plan what the technicians have to do tomorrow, to contact contractor or supplier to have a look, and to do fucking stupid things for the "compliance" and "standards".

[Anonymous No.9983896]

>>9983696
does it pay well?
I'm about to fail my engineering degree and end up working at a local hardware store for pennies.

[Anonymous No.9984178]

>>9981512
I really like the SDRPlay RSP series, choose model depending on needs. But for basic radioastronomy and satellite comms, you'd be fine with the RSP1a model with one input.

rtl-sdr.com is a really good site related to this kind of business, and a lot of the people are helpful.

Best of luck, homie.

[Anonymous No.9984558]

>>9983896
I'm from Hong Kong so things may not be applicable. It pays better when you're graduate engineer. However, you most likely will not be promoted until someone above you retired/fired(which haven't had happened for 50+ years). When your university buddy became a manager at some other contractors or consultants and getting very good wage cheque, you are just a petty "senior" engineer. But well of course not many people can get promoted to manager.

[Anonymous No.9984619]

>>9981074
I'm just pointing out the argument for j because I is taken is silly since J is already taken to for a more general concept than I.

Anyway, about the exp(iwt) convention being dumb, think back to how you learned to translate 1D functions: if you have f(x), to shift it right by a constant c, you write f(x - c). Same things for the phase of a complex exponential. If you did it in a sane and intuitive way, you would use the exp(ikx - iwt) convention. However, since you ultimately are only interested in the real part when talking about physical fields, both conventions are mathematically valid. Using exp(-ikx + iwt) is just bizarre.

[Anonymous No.9984775]

>>9984619
>more general concept
I'd debate that actually, K and J are surface/volumetric current densities but I, current, is a flux - a scalar, regardless of whether you're talking about an instantaneous current or some kind of average current. As such, Engineers that work on waveguides and electrostatics are much happier to use J for currents of all kind as you'd say, but the argument for not using i stands when it comes to people whose bread and butter is circuit analysis.

As for the wave convention, that's what I though you'd say and I feel exactly the same way, using the same argument, but for exp(jwt - jkx). We deal with AC circuits before waves, at low enough frequencies to neglect the traveling nature of the wave and just assume the voltage is the same everywhere at a given instant of time, so the expressions are always cos(wt). Adjusting for traveling waves, I suppose we just take our understanding of adjust the phase depending on what displacement we're considering. Maybe you do the reverse?

One last point to consider is that some engineering texts will use a sine basis for complex waves (which I dislike, but..), in which case you keep the imaginary part for the physical field. Using (x - t) means you'd need to bookkeep one additional negative sign between real and complex domains in that case.

[Anonymous No.9985459]

>>9982248
From what I heard, Im an EE undergrad but they don't really teach complex quantum stuff, is that the magnetic and electric field don't really exist and the phenomena that we ascribe to them is the exchange of muons between quarks. I wonder if this could be exploited to transport power across large gaps. I am still quite ignorant on the matter however...

[Anonymous No.9985464]

Is calculus important to an EE?
What can I get out of 3D Vector Calculus that w uould be important? It feels like I'm wasting my time in this class. I mean, I'll still try to get a good grade, but it feels pointless.

[Anonymous No.9985511]

>>9984775
I isn't a scalar, it's a vector. The magnitude of I is a scalar, but in 3D space, I requires a direction, even if it's a 1D current.

[Anonymous No.9985635]

>>9985464
Without a good understanding of Vector Calculus RF and Photonics is probably going to go over your head. Doesn't mean you can't do well at electronics and embedded systems tho.

>>9985511
That's not correct. I is a scalar, because it's a flux. The direction of the flux is necessarily defined by the surface normal it's flowing through, not by flux itself. For example, the current density in some region of space might point in a handful of directions, but you won't know how much current is flowing in one of those directions unless you pick the surface you're interested in and integrate over it. Or, consider the Biot-Savart law; the 'direction' of the current is defined by the vector curve defining its path of travel, but I is still a scalar there.

[Anonymous No.9985731]

>>9984178
Thanks m8

[Anonymous No.9985855]

>>9985635
>the current is defined by the vector
>but I is still a scalar there
sure thing, boss

[Anonymous No.9985951]

>>9985855
>t. brainlet

[Anonymous No.9986375]

is anyone here a physics/EE double major? What are some ideal careers for people studying both?

[Anonymous No.9986460]

>>9986375
double major is for people whose first major was not good enough. focus on grades internships and research

[Anonymous No.9986471]

>>9985951
you don’t green text
t. x
brainlet

[Anonymous No.9988246]

>>9985464
You at your course roster and see if you have a class in there that talks about "fields".

[Anonymous No.9988248]

Bump

[Anonymous No.9988259]

I'm an undergraduate studying EE here in the states, junior year right now. I have an internship with the transmission system protection department of a large electric utility. I'm about to start doing research on industrial drive control for a professor, should be interesting. I'm absolutely loving the field.

[Anonymous No.9988267]

>>9986375
My girlfriend is doing BS Engineering physics and MS EE. She's shown interest in RF but she's been enjoying her digital design courses.

[Anonymous No.9988294]

>>9984558
is engineering as saturated over there?

[Anonymous No.9989801]

Bump

[Anonymous No.9989946]

What's the nature of the electric field in a resistor/wire?
I know it's a consequence of J=σE, but that formula doesn't imply anything about the nature of E.
For example, I could just propel a bunch of electrons with a non electric force and create current (J), in which case E would be purely mathematical in nature.
Or, I could put them in an actual electric field to create the current, so the E in J=σE would be physically real.
If it's real, it's field lines are homogeneous and neatly go through the wire, no matter how the wire curves, turns and bends.
How does that work?

[Anonymous No.9989962]

>>9979103
Lowercase i is used for alternating current or changing direct current designated with a graph. To remove any missunderstandings we just use j.
It is a placeholder anyway, no need to get butthurt over it.

Better question to you physicists is why the hell did you designate the flow of current from + to - when only thing that really moves in current is electrons and they move from - to + and now we are stuck with shitty engineering practices and rules that we have to abide by just because your shit assumptions?

[Anonymous No.9990072]

>>9989946
>I know it's a consequence of J=σE, but that formula doesn't imply anything about the nature of E.
J=σE is Ohm's law (in local form) that describes drift currents i.e. currents that are due to electric field E.
In this case, you know the nature of E very well because E = J/σ. There is nothing more to it.
If σ is a tensor of rank 0 (a simple scalar) then E is a vector in the same direction of J scaled by 1/σ.
Rarely, if σ is a tensor of rank 2 (a matrix) E and J do not share the same direction.

That is if J is created only due to drift effect.
Obviously there are other thing things that affect current density J, e.g. diffusion current follows Frick's law: J=-Dφ'
If both are present then you have:
J = σE - Dφ'
Now if you know the constituent relation between E and D (i.e. D=εE where ε is a tensor like σ) and the current J, you can find E.

And there are other things that can cause the current to flow too e.g. simply by moving the object. These do not affect E, but do affect J.
You can model them with Jmove for example and then you have:
J = σE - Dφ' + Jmove.

>For example, I could just propel a bunch of electrons with a non electric force and create current (J), in which case E would be purely mathematical in nature.
Things that move electrons which isn't drift effect can be modeled *as if* they were produced by drift currents by looking at the effect as if it was moved by a ficticious electric field Ei. This is done because you get the ohm's law working again (disregarding Frick's law):
J = σE + Jmove
J = σE + σEi (Ei = Jmove/σ)
J = σ(E + Ei)
J = σEmodel
Emodel in this case in this case is purely mathematical in nature like you say. Your pushing would affect it, however it would not affect the original E field. The real E field is only affected by charge density and magnetic induction (gauss' law and faradey's law).

[Anonymous No.9990143]

>>9989962
>To remove any missunderstandings we just use j
this is a lie, because current density J exists

>Better question to you physicists is why the hell did you designate the flow of current from + to -
because at the time no one had figured out how to determine what the charge carrier in metal was. Moreover, in chemistry there are reactions where both negative and positive charge act as charge carriers, and in those situations, their is no clearly superior convention.

[Anonymous No.9990155]

>I know it's a consequence of J=σE, but that formula doesn't imply anything about the nature of E.
J=σE is Ohm's law (in local form) that describes drift currents i.e. currents that are due to electric field E.
In this case, you know the nature of E very well because E = J/σ. There is nothing more to it.
If σ is a tensor of rank 0 (a simple scalar) then E is a vector in the same direction of J scaled by 1/σ.
Rarely, if σ is a tensor of rank 2 (a matrix) E and J do not share the same direction.

That is if J is created only due to drift effect.
Obviously there are other thing things that affect current density J, e.g. diffusion current follows Frick's law: J=-diff * φ'
If both are present then you have:
J = σE - diff * φ'

And there are other things that can cause the current to flow too e.g. simply by moving the object. These do not affect E, but do affect J.
You can model them with Jmove for example and then you have:
J = σE - diff * φ' + Jmove.

>For example, I could just propel a bunch of electrons with a non electric force and create current (J), in which case E would be purely mathematical in nature.
Things that move electrons which isn't drift effect can be modeled *as if* they were produced by drift currents by looking at the effect as if it was moved by a ficticious electric field Ei. This is done because you get the ohm's law working again (disregarding Frick's law):
J = σE + Jmove
J = σE + σEi (Ei = Jmove/σ)
J = σ(E + Ei)
J = σEmodel
Emodel in this case in this case is purely mathematical in nature like you say. Your pushing would affect it, however it would not affect the original E field. The real E field is only affected by charge density and magnetic induction (gauss' law and faradey's law).

[Anonymous No.9990158]

>>9990155
>>9989946

[Anonymous No.9990317]

>>9990155
>mfw just barely passed EM last year
>too scared to revisit it because I'm a total fucking brainlet

[Anonymous No.9990350]

EE-anons, mech here with a question.
You know how you can program electromotors with boards like Arduino? What would you use if you wanted to program say, a servomotor for use in a digital camera or a dc actuator for use in an aircraft? What programming language is commonly used for such serious applications?

[Anonymous No.9990357]

>>9990350
you use python with ROS nodes usually

[Anonymous No.9990359]

>>9990350
what's wrong with just using something like an arduino and C?

[Anonymous No.9990377]

>>9990357
Python? Seriously? Isn't that a meme language?
>>9990359
Something tells me Airbus isn't going to use an Arduino to control its systems, probably because of reliability issues.

[Anonymous No.9990383]

>>9990377
>Isn't that a meme language?
Did you hear that on /g/ or something? Python is useful and easy to learn.

[Anonymous No.9990387]

>>9990377
>Python? Seriously? Isn't that a meme language?
Why do you think that? Most scientists use it.

[Anonymous No.9990391]

>>9990377
microcontroller + (carefully debugged) custom code is about as reliable as you get. A full fledged computer and operating system is probably used in some modern systems, but introduce far more points of failure.

for agencies like NASA, with mission critical code, they follow certain programming guidelines to prevent crashes (for instance, no recursive programs, no malloc(), etc.). hardware redundancy is also important, because radiation can and does damage semiconductor devices.

airbus probably isn't using an arduino, but the core of many commercial microcontrollers is just an ARM that's hooked up to mission specific hardware.

[Anonymous No.9990392]

>>9990377
>Isn't that a meme language?
just because something is a meme doesn't make it bad.

[Anonymous No.9990419]

>>9990383
lol no
No one uses Python in industry. For any serious project you use either C or C++ .

[Anonymous No.9990494]

>>9990419
>what is machine learning

[Anonymous No.9990699]

>>9990494
>serious project
Yes, please give me your (you).

[Anonymous No.9990824]

>>9990143
>because current density J exists
that is uppercase J, not lowercase j

>their is no clearly superior convention
>their
And I thought physicists were smart.

[Anonymous No.9990833]

>>9990419
>No one uses Python in industry.
Except for Google, PayPal, eBay, OpenStack....
Why don't you just go back to >>>/g/

[Anonymous No.9991096]

>>9990391
why no malloc? what do they use instead?

[Anonymous No.9991922]

>>9991096
Not that anon, but when using malloc in a large project, you are guaranteed to have memory leaks, while in space memory is extremely rare. I don't know how they do it, but I think well defined structure and scope can help.

[Anonymous No.9991933]

>>9991922
But what if the size of your arrays is not known at compile time, but only a runtime?

[Anonymous No.9993328]

>>9991933
you design your code so malloc isn't required. That means a lot of statically declared arrays, which requires knowing your specific application very well. generally people have a good idea of what the systems need to be doing in these contexts (you don't launch a rocket unless you know damn well the parameters of your mission)

[Anonymous No.9993348]

When are you fucking faggots going to start harnessing electricity from the stars? They're local.

Also, electrons aren't real.

[Anonymous No.9993571]

>>9991933
Just as you did in HS. Declare a big (for you) array.

[Anonymous No.9993576]

>>9993328
>>9993571
So how do you statically declare your arrays onto the heap rather than the stack?

[Anonymous No.9993712]

>>9978929
>>9978959
ok i figured it out

I want to do something related to cryptology

EE nerds, im going to get 1 billion starting salary

[Anonymous No.9993729]

I have an EE degree mostly power and control oriented (with some electronic engineering classes). I am not american and the degree takes 5 years. Can i get into an embedded systems master even if my EE degree is power oriented?

[Anonymous No.9993962]

What are some outdoor focused fields for an E.E, anything as long as its physical. I don't want to fucking sit anymore, I have forearm, back, and hip issues already and I swear to god, just no

[Anonymous No.9994458]

>>9993962
electrician?

[Anonymous No.9994543]

>>9980133
yes, your GPA doesn't fucking matter and there will always be places which will accept you even if you suck at school

[Anonymous No.9994567]

>>9993729
See what the pre-reqs are and how much you need to remediate. Difference between EE specialties is just a few courses,

[Anonymous No.9994633]

>>9994543
thank god. I just hope to restore some of the GPA to it doesn't look TOO bad.

[Anonymous No.9994755]

>>9978789
Im taking my first course in electronics and we have to build a power supply for a project.
Any good resources for this?
Im a complete beginner.
Until now ive only taking theoric courses.

[Anonymous No.9995178]

Studying signals and systems this semester, what assraping am I in for?

[Anonymous No.9995435]

What are the memefields in EE and related (even including a bit or some CS) that allow you to make something remotely interesting whilst making some bank (enough to buy a 200k usd home or something) relatively quick.

Also, what's better for EE research in general, academia or private R&D?
I know my questions are too broad but I'd like people to chime in and give their experience or anything really.

[Anonymous No.9996230]

>>9995435
better in terms of what? you're always going to make more money in industry with very few exceptions, but you'll probably have more freedom in academia. i work in govt research