Welcome to /r/ElectricalEngineering!

Hi, I recently have been offered a grad position at kirby group, but little information was given by kirby on what exactly my role will be, just wondering if anyone here had worked for kirby before.

Ok so i have a phone that died (motherboard issue). And idk why it only charged while the phone was alive. the phone is currently out of battery (is the only screen that appears), is there a (budget) way to charge the battery manually?

https://preview.redd.it/rsgm2i6ew1yd1.png?width=756&format=png&auto=webp&s=3e31069e7e969e16cf05c3140e43f35b2434c97a

This is the first time I have encountered a situation where one of the terminals isn't connected to ground. How do I go about finding the thevenin circuit for this? Thanks!

Hi All,

I have a 1mW, 650nm collimated laser that I want to measure using a photodiode.

The laser's operating frequency will be very low—essentially DC—but I would like the design to support frequencies up to 1kHz.

I based my design on a document from TI.

The voltage reading range is 0.1V (to avoid the op-amp going into low rail saturation) to 4.9V. The photodiode in use is the ODD-1W.

I would appreciate your feedback on the design and component selection. Attached are some images from the LTSpice simulation.

Thank you,

https://preview.redd.it/8heoxv68m1yd1.png?width=1905&format=png&auto=webp&s=33fd5f9367c8999bd6c8424cb25e3cb4e7da6de6

This might be an puerile question. I barely have time to do one book fully. I picked up Fundamentals of Electric Circuits and that book is massive. I have books like Introduction to Electrodynamics lined up to do along with that.

Do we or you guys read everything cover to cover and solve all problems?

The offending circuit :(

I started by turning the current source I1 and R1 on the left into a voltage source and resistor, but I don't think that's correct.

I can also see possibly using the combined KVL KCL technique on nodes Vx and Vy, but I keep getting incorrect answers and I'm not sure if that's with my approach or just working out.

Any tips would be greatly appreciated!

This is the question, the answer isn't -0.21mA or 0.21mA

My working out

I'm not sure what I'm doing wrong, I built the circuit in a simulator and it gave Ir1 as 0.21mA as well. Thanks in advance!

So I just started AC and I notice when I change my answer to decimal and try to find V like the left side my answer is wrong while if I keep it likr the right side it is correct? and I couldnt spot any mistake while changing it to decimal so this doesnt make sense to me. I was wondering if anyone can see why?

I've been trying for days to control a Boost converter connected to a solar panel through simulation. I’ve failed in numerous attempts, and my question is whether there's an easier way to do it. From what I've read, it's not possible to obtain a direct relationship between the input voltage and the duty cycle, that is, the transfer function Vin(s) / d(s).

Because of this, I opted for a cascade control approach. Through the MPPT algorithm, I generate the voltage reference needed for the panel to operate at the maximum power point (MPP). Then, I use the DC link relationship, where there is a capacitor, that is, Vc(s) / ic(s), which is equivalent to Vpv(s) / ic(s). From there, I apply Kirchhoff's Current Law (KCL) to obtain the current reference in the inductor and use iL(s) / d(s). This is the approach I’m following, but it’s not giving the expected results.

Therefore, I’m asking if there’s a more direct way to do it or if there’s something else I should consider.

Hey everyone!

Can you please help me understand some of the fundamental concepts? I am truly struggling to grasp them:

So we have the Coulombs Law:

F = Ke x (q1 x q2)/dˆ2

This is very intuitive to me because of gravitation, I can easily understand how two charges exert a force to each other and that such force diminishes as we increase the distance they are placed apart.

I start to struggle when we insert the electric field:

E = F = Ke x (q1 x q2)/dˆ2

We want to isolate q1 to see how it exerts a force in the space around it, okay:

E = F/q2 = ke x q1/dˆ2

So we have that the strength of the electric field q1 is generating in a given point is given by:

E = ke x q1/dˆ2

We also have that the force another charge experience at said point is given by:

E = F/q2 -> F = E x q2

So as long as we have stablished a point in space, we can calculate the strength of the electric field at said point and, therefore, calculate the force a charge at said point will experience.

One of the problems I start to get is to understand why the electrical field is overall constant in a circuit if it evidently depends on the distance from the source (positive terminal)... A charge near the positive terminal should experience a much greater "pull" force than a charge at the negative terminal.

I mean, we literally need to use the distance:

E = ke x q1/dˆ2

A charge_1 near the positive terminal should be "pulled" with a greater force than a charge_2 near the negative terminal, because the charge_1 has a smaller distance from the source of the field, which by E = ke x q1/dˆ2 means the electrical field there is stronger and, therefore (F = E x q2 ), the force has to accordingly be "stronger"/"bigger" than that of charge_2.

Then it seems Voltage starts to play a role in this all... And I am really struggling to understand the difference of voltage in relation to the electrical field.

Textbook definition of voltage is "the difference in electric potential energy per unit charge between two points in the circuit. It tells how much energy a charge would gain or lose if it moved from one terminal of the battery to the other"

Then I was like, okay... Voltage talks about energy whereas electric field talks about force... Okay, to the basics, let's check energy and work:

W = F.d (assuming the cosΘ = 1)

The above is, again, very intuitive to me to understand what it is describing.

We deduced the electric force before -> F = E x q

So far so good.

W = E x q x d (with the substitutions), where W is the work (energy transferred), q is the charge experiencing the electrical force (the "pull"), and d is the distance... Then I was like, okay, what distance is this? We already looked at a distance before when analysing the strength of the electrical field. But here are we even talking about a different distance(?), it is the distance through which the charge moves under the electrical force.

So I deduced that in a circuit the maximum work a charge can do (or rather the maximum energy a charge can transfer) is given by the electrical force (E x q) through the entire distance (d) between the negative terminal and the positive terminal.

Okay, hold on... this is starting to get out of hands. Lets organise ourselves:

1 - The energy a charge can transfer depends on:

\-> The electrical field (E = ke x q1/dˆ2)

\-> the charge itself (q)

\-> the distance (d) said charge moves, so if the charge moves all the way to the positive terminal, that would be precisely the same distance used to calculate the electrical field.

hmmmm... okay, okay...

What was the textbook definition of voltage again? "the difference in electric potential energy per unit charge between two points in the circuit". So we have two points there well defined - one is where the charge is, the other is where the positive terminal is.

Fine.

Now - "the difference in electric potential energy per unit charge".

okay, so:

V = ΔW / q (the variation of energy/work[W] divided by the charge[q])

Okay, okay... So:

ΔW = V x q -> basically: W = V x q

if we go back, we had:

W = E x q x d

And now we have

W = V x q

So:

V x q = E x q x d -> So V = E x d...

V = E x d

Voltage then is... what??? The sum of the variations of the electric field between the location where the charge is and the positive terminal? Is that it?

We had earlier that F = E x q... So E = F/q

Therefore:

V = (F x d) / q .... which makes absolute sente, right? V = ΔW/q

But what am I reading? What that maths mean?

We have that:

E = F/q

and that

V = W/q

But what they even mean?

I mean... I am kind of deducing that the Electric field is the strength of the pull the charge experiences, and that the further away from the positive terminal the waker it gets. While the voltage I am deducing as being the total amount of energy a charge can transfer if moved from its position all the way towards the positive terminal.

When we have a 5v battery, then the 5v only happen if a charge actually leave the negative terminal and move all the way to the positive terminal?

A charge (the electrons) in the middle of the copper wire would then only produce 2.5V?

Why do I get all the 5V in the circuit if a charge actually moves very slowly through the conductor? I mean, it should take hours until we actually have charges leaving the negative terminal and arriving at the positive terminal...

The electrical field produced by the positive terminal pulls all the electrons in the circuit, but why doesn't it get weaker near the negative terminal (according to the textbook) if it depends on the distance?

Man this is all soooooo confusing!!!

I mean.... If V = E x d, and d varies across the circuit then how can we have a constant voltage AND a constant electrical field?

Oh boy... this makes me feel like I should have gone into Law school instead hahahaha

The biggest ever thank you to those who can help me out here, grasping those concepts is so difficult!

TLDR: I have a math undergrad - can I work as an engineer or should I go back to school?

Hey, I graduated from a math undergrad degree last year, and I realized a lot of the jobs I want to do are engineering related.

Do you think it's worth to go back and do an engineering degree right after a bachelor's, especially one from STEM? I've looked into working with PLCs, as a radiofrequency engineer, or with embedded systems. I'm sure there are even cooler subfields within electrical that require a lot of technical knowledge and hands-on work. I don't know the industry well enough but does a math degree hold weight in fields like these, or in other engineering fields? Would I be able to find work in these areas or would it be better if I went back for a degree. I know I will learn on my own, but I would like to be employable.

I'm more worried about the degree being another 4 years. I'm 24 at the moment, so if I go back I'll be 29 or 30 when I graduate. I guess the age doesn't really matter. I enjoy learning for the fun of it so I'm very excited about the idea, but a bit worried about expenses, lack of work and real-world experience, and possible opportunity cost.

Can anyone provide some guidance on possibilities?

Just for reference, I worked a bank for a bit, did an accounting internship, and then currently work as a math tutor.

I'm a bit frustrated, but maybe it's just my ignorance on the matter. I recently went back to school to major in electrical engineering.

My frustration stems from having to take so many classes (that I know are beneficial) before I can start learning basic circuitry. I know a lot of basic circuitry only requires algebra, yet I have to wait until I pass differential equations to start doing anything that I'm interested in. Even though I understand that computer science is necessary as an engineer, I still don't get why I'm learning this before anything related to electronics.

I’m an electronics technician working for an embedded research company. I primarily do testing and rework. I’m very comfortable at analyzing circuitry to understand what I need to test and what can be modified but I’m very very weak at the actual design side of things. Recently I’ve began learning Altium and doing personal projects and I’m struggling with getting up to speed. I’m going part time for my undergrad but I was hoping for some resources from you guys. Thanks

Hey, I am a second year EE student who is trying to figure out what to specialize in. For some background about me, I have taken physics 1 and am taking physics 2 and an intro to semiconductors class. Additionally, I am volunteering in a quantum computing lab where I do data collection. (I think the research is interesting, but I am not really involved in that part, so I don't really have that much transferable experience.)

I am not sure what I would like to go into, just know that I could see myself doing this type of stuff for a long time. I have looked into medical imaging and instrumentation which is interesting. Is anyone working in a job with applied physics? If so, do you enjoy your work? How's the pay? How did you get into it? Thanks!

I hate that I get so nervous testing/interviewing that my mind draws a blank. I'm interviewing for a major company, a huge opportunity, and they're asking me RF questions. Tell me why the hell did I blank when he asked me what 10dbm +10dbm is? lol I said well it would be 20 dbm, before I shouted "wait! I know this, I had just drawn a blank, I know you need to convert to power and then back to dbm and did the math to show ~13 dbm).

Holy crap, has anyone fucked up this bad during an interview regarding fundamentals?

Hello there, I want to know how is that part of being a ee , how that works, what type of jobs you could find , how hard is to get a freelance job , advice and opinions!

I have an upcoming interview for the failure analysis engineer at Texas Instruments. Are there any specific topics I should freshen up on? Thanks in advance!

Hi im a 17 year old junior in high school and at this point in my life like most I have been trying to figure out what I want to do with my life and what I want to go to school for. In my high school we have an energy class it was a Harder class for me because of all the notes we had to take and all the different types of energy forms we learned but I end up really liking it I did some research and so I settled for electrical energy as my goal I have been trying to set my self up with higher level, math classes and more advanced electrical classes and also some dual credit college classes for electrical technology. Although I am really interested in electric engineering I am at a point where I don’t know if I really can do it I feel like the people who succeed in this type of field are just naturally smart and gifted people on the other hand I have a habit of doing the bare minimum while still passing I guess I just get lazy. I don’t know. I’ve been trying to break the habit because I really want to succeed in life. My family doesn’t have much money so I feel like I don’t have any room for mistakes After high school I feel like I need to be kind of that golden goose of the family if that makes sense someone who pulls us out of there. But aside from that, I just don’t know if I can. I feel like it might be too much math or just a lot in general and I just don’t know where to start if anyone has any advice on What can I do to prepare myself for electrical engineering what I classes I should take, websites or just anything that will help me out to reach this goal for becoming an engineer that would be much appreciated.

But I want to know what did you do? How did you get where you’re at now? (Detailed)

Hi everyone,

As the title says, I'm currently in first year of Electrical Engineering at Concordia University, Montreal. I'm looking for certifications related to my field that I can obtain now and can be useful for my future internships. Any recommendations would be appreciated. Thanks a lot.