jhoward@helps.cactus.org (James Howard) (04/30/91)
In math the sqrt(-1) is representated by the letter i. In electronics why is the letter j used to represent the square root of -1? Thanks for any replies, posted or Emailed. --- James Howard Howard Electronic Laboratories Products & Services AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org
oistony@ubvmsd.cc.buffalo.edu (Anthony Petro) (04/30/91)
In article <1139@helps.cactus.org>, jhoward@helps.cactus.org (James Howard) writes... > >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? > >Thanks for any replies, posted or Emailed. the explanation i've been given is because i in electronics is too often used to refer to instantaneous current, and j was the next logical and relatively trouble-free choice... > >James Howard Howard Electronic Laboratories Products & Services >AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org anthony m. petro "beethoven" i can say what i want; i'm just an undergrad oistony@UBVMSD.BITNET "frame by frame, oistony@mednet.bitnet death by drowning, petro@sun.acsu.buffalo.edu in your own in your own... analysis..."
bobw@col.hp.com (Bob Witte) (04/30/91)
>/ col:sci.electronics / jhoward@helps.cactus.org (James Howard) / 4:12 am Apr 30, 1991 / > >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? > >Thanks for any replies, posted or Emailed. > >--- > >James Howard Howard Electronic Laboratories Products & Services >AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org >---------- Possible answers: 1) To confuse math majors and keep them out of EE. 2) sqrt (-1) had to be j because i is used for current Why isn't c used for current? Because c is used for capacitance. -------------------------------------------------------------------- Bob Witte HP Colorado Springs Division bobw@col.hp.com P.O. Box 2197 Phone:(719) 590-3230 Colorado Springs, CO 80901 Radio: KB0CY "Of course, then again, I've been wrong before." --------------------------------------------------------------------
rabbit42@matt.ksu.ksu.edu (Bruce McLaren) (04/30/91)
jhoward@helps.cactus.org (James Howard) writes: >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? >Thanks for any replies, posted or Emailed. >--- >James Howard Howard Electronic Laboratories Products & Services >AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org The explanation I've always heard is that i is already being used to represent current. That is the _I_ntensity of current. I've always assumed that i for current intensity was made up after the fact. Why is i used for current? -- Bruce McLaren | There is no problem too big rabbit42@matt.ksu.ksu.edu (for most stuff) | to run away from mclaren@eesun1.eece.ksu.edu (for work) | rabbit42@ksuvm.ksu.edu (if all else fails) \|/
betel@buhub.bradley.edu (Robert Crawford) (04/30/91)
jhoward@helps.cactus.org (James Howard) writes: >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? It has to do with the assignment of "direction vectors". I.e. 8i + 4j is 8 units along the x-axis and 4 units along the y-axis. Now, if you look at the complex number plane, the imaginary part is graphed along the "y-axis". The use of i comes from an abbreviation for "imaginary". j is a better term, since you can then treat complex numbers as vectors and do cross and dot products... -- Rob Crawford \"You can have peace. Or you betel@buhub.bradley.edu \can have freedom. Don't ever Dum vivimus, vivamus! \count on having both at once." -- Rob Crawford \"You can have peace. Or you betel@buhub.bradley.edu \can have freedom. Don't ever Dum vivimus, vivamus! \count on having both at once."
crean@zds-oem.UUCP (Pat Crean Federal Systems Engineering x ????) (05/01/91)
i was already used to designate current (e=ir).
sidney@coed.coastal.ufl.edu (05/01/91)
> >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? > >Thanks for any replies, posted or Emailed. > The letter i is used to represent current flow in Electrical Engineering ie. E=I*R so another letter character is needed to represent sqrt(-1) and j was chosen.
mallick@ethiopia.crd.ge.com (john a mallick) (05/01/91)
To add more fuel to the fire, I seem to recall that someone once mentioned that i = -j ; both still have the property that i^2 = j^2 = -1. There seemed to be this disconnect between the engineers and the physicists regarding how to use complex exponentials to represent sinusoids. The engineers (at least EE's) use exp(j*wt) = cos(wt) + j sin(wt) and you get sin(wt) by either using Im(exp(j*wt)) or Re(-j*exp(j*wt)). The physicists prefer to stay away from the Imaginary-part-of stuff and stick with Re(i*exp(-i*wt)). It all depends where you like to put the - sign. Maybe this should go to alt.folklore.physics... John Mallick WA1HNL
touch@gradient.cis.upenn.edu (Joseph D. Touch) (05/01/91)
(why is 'i' used in math, and 'j' in EE, both for SQRT(-1)...) In article <38610010@col.hp.com> bobw@col.hp.com (Bob Witte) writes: > Possible answers: > 1) To confuse math majors and keep them out of EE. > > 2) sqrt (-1) had to be j because i is used for current > Why isn't c used for current? Because c is used for capacitance. > OOOPS - isn't 'c' already used for the speed of light? So many constants, so few characters. [Physics, EE, etc] is the eternal struggle to convert 'fudge factors' into universal constants - and get your name on them! - Joe Touch (yup - like I got my name on this quote!)
depolo@eniac.seas.upenn.edu (Jeff DePolo) (05/01/91)
In article <1139@helps.cactus.org> jhoward@helps.cactus.org (James Howard) writes: >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? The way I heard it, it's to keep EE's from confusing it with current (I). --- Jeff -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Jeff DePolo N3HBZ/AE Twisted Pair: (215) 386-7199 depolo@eniac.seas.upenn.edu RF: 146.685- 442.70+ 144.455s (Philadelphia) University of Pennsylvania Carrier Pigeon: 420 S. 42nd St. Phila PA 19104
pjh@mccc.edu (Pete Holsberg) (05/02/91)
In article <38610010@col.hp.com> bobw@col.hp.com (Bob Witte) writes:
= Why isn't c used for current? Because c is used for capacitance.
Actually, C is used for capacitance.
Pete
--
Prof. Peter J. Holsberg Mercer County Community College
Voice: 609-586-4800 Engineering Technology, Computers and Math
UUCP:...!princeton!mccc!pjh 1200 Old Trenton Road, Trenton, NJ 08690
Internet: pjh@mccc.edu Trenton Computer Festival -- 4/20-21/91horner@hpdtczb.HP.COM (James G Horner) (05/02/91)
> >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? > >Thanks for any replies, posted or Emailed. > >--- > >James Howard Howard Electronic Laboratories Products & Services >AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org According to my old college circuit book, _Engineering_Circuit_Analysis, by Hayt and Kemmerly, the j is used to prevent confusion with the symbol for current, i. Jim Horner
gordond@hpmwtd.HP.COM (Gordon DeWitte) (05/02/91)
To avoid confusion with the "i" that is used to represent current.
jpat@hpsad.HP.COM (Jeff Patterson) (05/02/91)
Because "i" is reserverd for current -Jeff
ayman@zip.eecs.umich.edu (Ayman Kayssi) (05/02/91)
In article <1991May1.170325.28926@mccc.edu>, pjh@mccc.edu (Pete Holsberg) writes: |> In article <38610010@col.hp.com> bobw@col.hp.com (Bob Witte) writes: |> = Why isn't c used for current? Because c is used for capacitance. |> |> Actually, C is used for capacitance. |> |> Pete c is used for capacitance per unit (length/area/volume) I (or i) is used for current following the French who use I to denote : "L'Intensite' du courant" or "the current Intensity". - - So in French EE textbooks, the problem would be to find, specifically, the current Intensity, as opposed to US textbooks, where the statement of the problem would be something like: "find the current", which is not as accurate. -- [ Ayman Kayssi | Email: ] [ Advanced Computer Architecture Lab. | ayman@engin.umich.edu ] [ EECS Dept., Univ. of Michigan, Ann Arbor | ayman@eecs.umich.edu ]
jecome01@ulkyvx.bitnet (05/04/91)
In article <1139@helps.cactus.org>, jhoward@helps.cactus.org (James Howard) writes: > > In math the sqrt(-1) is representated by the letter i. In electronics > why is the letter j used to represent the square root of -1? > > Thanks for any replies, posted or Emailed. > The letter i is commonly used to represent current, thus inorder to keep the confusion to a minimum, the letter j is used instead. No big deal.
conger@hpcupt1.cup.hp.com (Edward Conger) (05/04/91)
>/ hpcupt1:sci.electronics / bobw@col.hp.com (Bob Witte) / 7:47 am Apr 30, 1991 / >>/ col:sci.electronics / jhoward@helps.cactus.org (James Howard) / 4:12 am Apr 30, 1991 / >> >>In math the sqrt(-1) is representated by the letter i. In electronics >>why is the letter j used to represent the square root of -1? >> >>Thanks for any replies, posted or Emailed. >> >>>--- >> >>James Howard Howard Electronic Laboratories Products & Services >>AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org >>---------- > Possible answers: > 1) To confuse math majors and keep them out of EE. > > 2) sqrt (-1) had to be j because i is used for current > Why isn't c used for current? Because c is used for capacitance. > >-------------------------------------------------------------------- >Bob Witte HP Colorado Springs Division >bobw@col.hp.com P.O. Box 2197 >Phone:(719) 590-3230 Colorado Springs, CO 80901 >Radio: KB0CY >"Of course, then again, I've been wrong before." >-------------------------------------------------------------------- 'c' isn't used for the flow of charge carriers because the person who created the term didn't use an >>English<< word. An amusing parochiality, neh? "I" is short for "Intensite'" - a French word.... -Ed. An EE, though I play a CS nerd on TV.
moonhawk@bluemoon.uucp (David Culberson) (05/04/91)
pjh@mccc.edu (Pete Holsberg) writes: > In article <38610010@col.hp.com> bobw@col.hp.com (Bob Witte) writes: > = Why isn't c used for current? Because c is used for capacitance. > > Actually, C is used for capacitance. > > Pete > -- > Prof. Peter J. Holsberg Mercer County Community College > Voice: 609-586-4800 Engineering Technology, Computers and Math > UUCP:...!princeton!mccc!pjh 1200 Old Trenton Road, Trenton, NJ 08690 > Internet: pjh@mccc.edu Trenton Computer Festival -- 4/20-21/91 Nitpicker. This is from moonhawk@bluemoon.uucp moonhawk%bluemoon@nstar.rn.com who doesn't have their own obnoxious signature yet
pjh@mccc.edu (Pete Holsberg) (05/08/91)
In article <q5oF22w164w@bluemoon.uucp> moonhawk@bluemoon.uucp (David Culberson) writes: =pjh@mccc.edu (Pete Holsberg) writes: = => In article <38610010@col.hp.com> bobw@col.hp.com (Bob Witte) writes: => = Why isn't c used for current? Because c is used for capacitance. => => Actually, C is used for capacitance. => = = Nitpicker. = No, just "case-sensitive"! ;-) Pete -- Prof. Peter J. Holsberg Mercer County Community College Voice: 609-586-4800 Engineering Technology, Computers and Math UUCP:...!princeton!mccc!pjh 1200 Old Trenton Road, Trenton, NJ 08690 Internet: pjh@mccc.edu Trenton Computer Festival -- 4/20-21/91
gomez@speedway2.DAB.GE.COM (Frank Gomez) (05/08/91)
In article <1139@helps.cactus.org> jhoward@helps.cactus.org (James Howard) writes: > >In math the sqrt(-1) is representated by the letter i. In electronics >why is the letter j used to represent the square root of -1? > >Thanks for any replies, posted or Emailed. > >--- > >James Howard Howard Electronic Laboratories Products & Services >AA5R cs.utexas.edu!helps!jhoward or jhoward@helps.cactus.org In electrical engineering the symbol "i" is used to imply current. Thus a new symbol "j" was chosen, as to not confuse people.
bob@miranda.inmos.co.uk (Bob Green) (05/10/91)
In article <q5oF22w164w@bluemoon.uucp>, moonhawk@bluemoon.uucp (David Culberson) writes: |> pjh@mccc.edu (Pete Holsberg) writes: |> |> > In article <38610010@col.hp.com> bobw@col.hp.com (Bob Witte) writes: |> > |> > Actually, C is used for capacitance. |> > |> > Pete |> |> Nitpicker. ^^^^^^^^^^ Not really, case is actually quite important. For example how much current would you prefer to sink, 5 mA or 5 MA ? -Bob -- | Bob Green Inmos Ltd, Bristol | EMail(UK) ukc!inmos!bob |---------------------------------------| or bob@inmos.co.uk |The opinions above are my personal | Internet: bob@inmos.com |views and do not reflect Inmos policy. | UUCP:(US) uunet!inmos.com!bob