Electrical Engineers, help me!

[exbass94]

I'm trying to do my analog circuits hw and I just cannot figure this out. We just started the chapter on AC circuits with impedance and phasors and crap. I have the solution to the problem right in front of me, but I don't understand how he went from one step to another in certain places.
For example, he had current as a function of time like this:

i(t) = 10cos(377t + 30*) Amps ("*" means degrees)
and then he converted that to this:

10|30* Amps

How did he do that?

Also, another problem I have is with the "j" that's used in complex numbers
He went from Z = (2 - j265.25)/(3 - j265.25)

to this Z = (265.25|89.56)/(265.25|89.35)

 

[Nipplechops]

He first tranformed the current from a time domain representation to a frequency domain representation. It simplifies circuit analysis greatly when dealing with non-DC sources.

Basically to do this you convert the time domain representation to frequency domain using Euler's Theorem (if I remember right). I can try and dig up my old notes to give a more clear explanation.

The impedance work is similar.

Let me see if I can find my old notes. That would help me give a clearer explanation!

 

[matt32]

wow have fun with that one, i wish i could help you. I had a circuit modeling class last semester....lets just say after i barley passed with a low "c" i switched my major to mechanical engineering, that phasor sh*t is what really got me

 

[Simple_serf]

Crap....It's been a long time since I have done any of that...

I found out very quickly that for what I do, the Theory I learned in the classroom doesn't help a whole lot when you are laying in a control panel replacing just plain worn out parts.

I'll see if any of it comes back to me at work tonight...

 

[Nipplechops]

Here is a link that explains the phasor transform quite well. Much better than I ever could with a keyboard. Basically it is a modified application on Euler's Theorem as I said before. Seems that the text in these forums is lacking in the symbol department.

http://homepages.udayton.edu/~hardierc/ECE203/phasors.pdf