AC Circuits / Alternating Current

[woodentsick]

Hi, PF :)

I was self-studying AC circuits, and my main goal right now is to understand impedance. However, before that, I was wondering how one would derive the formulas for alternating voltage (and current), namely [URL]http://upload.wikimedia.org/math/5/a/0/5a0ecaa1432c6cdce653a943b4962a21.png[/URL]

The textbook I borrowed from the library does not have derivations of the formulae :( They just write down the actual equation...

Thanks so much!

Woodenstick

 

[gomunkul51]

It is so because alternating voltage is created by Electromagnetic Induction, basically by spinning a coil inside a magnetic field. This delivers voltage in the form of a sine wave.

If you want to understand how it is created, study "Electricity and Magnetism".
If you don't know it yet, I highly advice you to do so. It is a beautiful theory and very practical!

Great video lactures from Prof. Walter Lewin (MIT):
http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/video-lectures/

http://en.wikipedia.org/wiki/Electromagnetic_induction

 

[woodentsick]

Hey, thanks for your reply!

I looked at some of the MIT videos, and they were very informative, but as far as I know they don't cover the derivations of the equations for alternating current/voltage :(

 

[gomunkul51]

Hey, thanks for your reply!

I looked at some of the MIT videos, and they were very informative, but as far as I know they don't cover the derivations of the equations for alternating current/voltage :(

I've already gave you a basic explanation why it's a sine (because it's spinning) :)

It is so because alternating voltage is created by Electromagnetic Induction, basically by spinning a coil inside a magnetic field. This delivers voltage in the form of a sine wave.

But nevertheless Prof. Lewin does have a rudimentary explanation in one of the videos and I think this is exactly what you are looking for.

http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/video-lectures/lecture-17-motional-emf-and-dynamos/

P.S. congratulations! you will know how electricity is created.