Question about Resistance for EE's.

[Immacomputer 10+ year member]

Well, semiconductor implies that current will flow well one direction but if you reverse the direction it will not flow, or only very little will flow, a resistor for the most part has no polarity meaning it is not a semiconductor technically.

That's more of a definition of a diode and not all semiconductors. Semiconductor devices are referred to as devices created using silocon and other similar elements to get different effects from the device.

 

[seg_representin 10+ year member]

It's fun stuff but some of it is hard as hell and very tedious. Depending on the school, you will learn the physics behind the semiconductors in a pure semiconductors class or in your circuit design class. I took a separate course for it and we cover it in less detail in the circuit design course. In the design course, we mainly focused on transistors and the physics behind them for use in circuits. So far, the semiconductor physics course has been on of my favorites in the EE path at my school. I will probably take the grad level semiconductor fabrication course for a tech elective in one of the next few semesters.

I was going to go to the university of illinois, but as of right now i want to play baseball in college. I've had arm problems for the past 8 months, so when i went to scouting showcases i could only hit and not throw. I'm pretty sure i'm going to go to a junior college and play baseball for a couple years and then transfer over to a division I and play. Id love to go to illinois, but i have heard its pretty much impossible to play a sport and go through the engineering department.

 

[bose301s 5,000+ posts]

That's more of a definition of a diode and not all semiconductors. Semiconductor devices are referred to as devices created using silocon and other similar elements to get different effects from the device.

Yea, lol, just read that in my electromagnetics book. That class is fvcking hard, not a fan of it.

 

[bose301s 5,000+ posts]

I was going to go to the university of illinois, but as of right now i want to play baseball in college. I've had arm problems for the past 8 months, so when i went to scouting showcases i could only hit and not throw. I'm pretty sure i'm going to go to a junior college and play baseball for a couple years and then transfer over to a division I and play. Id love to go to illinois, but i have heard its pretty much impossible to play a sport and go through the engineering department.

It's like that at pretty much every engineering school, engineering is about the hardest thing you can do, and EE is one of the hardest engineering fields.

 

[Immacomputer 10+ year member]

Yea, lol, just read that in my electromagnetics book. That class is fvcking hard, not a fan of it.

I think I might take it next semester and I'm not looking forward to it at all. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[ngsm13 5,000+ posts]

Lol @ some of this shit...

nG

 

[Lakota 5,000+ posts]

Lol @ some of this shit...
nG

lol @ an EE dropout.

 

[thch 10+ year member]

To the main topic, the actual use of resistors is not as interesting/useful as the concept of resistance. resistance = work using element. this gives rise to concepts like "resistance, as seen by X". eg, input and output resistances of an amplifier, which may be different than any physical resistor in the circuit. for example, a motor spins. applying a MECHANICAL load will cause the motor to draw more current. the 240V AC line stays fixed at 240V, thus the motor APPEARS to have a lower resistance. This is 100% correct -- the mechanical load uses energy that came from the 240V line!

eg, the input resistance of an emitter follower is possibly 100 times higher then the resistor used in the circuit. To apply a voltage across this resistor, the majority of current comes from ANOTHER power source (battery), and thus you have less current for a given voltage = higher inputer resistance.

and the output resistance of this circuit is also lower then any series resistance the source might have for the same reason -- if output current needed to increase, it would pull MOST of the current from the power supply NOT the source!

From here, ideas of the incremental resistance arise. This brings up the idea of "negative resistance". This only means that when the input signal increases, some OTHER power source forces a current back to the source. This applies to some oscillators where an RLC network (damped oscillator) is aided by adding some negative resistance to make the circuit into a full blown oscillator.

From there, the other amplifer types arise (transresistance - current to voltage, transconductance - voltage to current, voltage gain - voltage to voltage, current gain - current to current)

once concpets of reactance -- elements that store and release energy -- are added, you can start to see all kinds of interesting things.