Why do we use complex number?

Hi all,
I just wondering why do we study complex number. I know that we use it in application such as in analysis of circuit that contain passive device. Why don't use real number only......

Re: complex number

one of many reasons is that the behavious of L and C can not be defined by real numbers , they r depicted by complex nos.
and complex nos. are not limited to circuit ananlysis,
they are every where , u can find them in ctrls, in telecom and wat not and wat not

Re: complex number

bizoo said:

one of many reasons is that the behavious of L and C can not be defined by real numbers , they r depicted by complex nos.
and complex nos. are not limited to circuit ananlysis,
they are every where , u can find them in ctrls, in telecom and wat not and wat not

Click to expand...

Could you tell me what is the behaviours of L and C that cannot be defined by real number.... is it because of the phase for example....

Re: complex number

solving the RLC circuits using the differential circuits is terrible jobs... and complex number can solve it as well wth a simpler approach... so it is required...

not only in RLC circuits solving,,,

in control theory/sys.... stability stuff is dealt using complex num as well... poles and zeroes...

in those EM stuff... dealling wth signal/wave... complex num are also essential...

regards,
sp

Re: complex number

sp said:

solving the RLC circuits using the differential circuits is terrible jobs... and complex number can solve it as well wth a simpler approach... so it is required...

not only in RLC circuits solving,,,

in control theory/sys.... stability stuff is dealt using complex num as well... poles and zeroes...

in those EM stuff... dealling wth signal/wave... complex num are also essential...

regards,
sp

Click to expand...

Maybe one of the purpose like u said is to replaced something to make it simpler. But there is no physical meaning right? I would like to know how we relate the complex number with physical meaning. Why resistor doesn't have this complex number? And why do they call y axis imaginary number? Yes, we use this complex number in many application. I just want to know the reason why we use this number instead of real number. Even better if you could explain it in the physical meaning. thanks

Re: complex number

your curiousness is overwhelming... hahahha...

okok,, i try to explain... i might b mistake.. as it is been sometimes... but i do my homework... hehehhe

actually complex num hav physical meaning as well.... as u see... for impedance.... it is

Z=R+jXL and Z=R-jXc..... it do bring physical meaning....

as j is 90 degree f = jb(for example)... u can change to euler form...'b' is the magniude and the 'j' give the projection of 90 degree from +ve x-axis... how u get j is 90degree... tan-1(b/0)= 90degree....

when u use ohm law wth this kind of impendence(RLC) using complex number,,, u can get the phase diff...

like wad u get when u use oscillator to test the voltage/current phase(sin wave) in the circuits... hope this make u see the physical meaning of complex number... it carries lot of physical meaning...

in EM, communication stuff(wad i hate... complex num shows more physical meaning if u hav study tht already... it even proof the physical meaning of weird wave using the complex number....

hope other can try explain to him... i cant. lack of skill to express myself...

when i was first year in my university... the lecturer giv a joke on complex number.. mention tht .....


but now, i know how wrong tht is... we use it all the time.... all the time...

regaqrds,
sp