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# 204

j - March 25, 2010
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Jreally?

Doesn't it depend on the field of study?

Yeah, that's the joke. They're making fun of the electrical engineer for using j (because i stand for current... or i guess "iurrent", lol).

Frankly, I never got the problem. In physics I use "I" for the current and "i" for the imaginary unit. How can it be so hard?

Most usually, in Electrical Engineering, capital letters represent values that are constant over time, while lowercase letters represent values that vary over time. Thus, “I” represents constant current, “i” or “i(t)” represents variable current, and you need something for the imaginary unit. (Underlined variables on the other hand are complex-valued.)

How do you guys deal with unit vectors?

(Haha, there's a maths test at the bottom to submit :D )

mine too!

with ^'s?

The i is from 'current Intesity!!!

Screw them, i is for loops :P

for(int i = 0; i if(i == Pwned(You))
lol();

Damn, my text got formatted >_

Screw them, i is for loops :P

for(int i = 0; i < var1;i++)
if(i == Pwned(You))
lol();

because I, an electrical engineer who loves math and physics need to make a distinction between AC and DC. You in fact use i for AC and I for DC. Using capital I for AC would confuse electrical engineers. But I had to painfully accept this convention. I too feel the same way but it would look really stupid writing something like i(t) = e^(iw*t)...

@Justin wait, you just confused me, isn't capital I also used for AC since that's how you denotate phasors?

I think the last sentence is more accurately: "Why don't you go and Jmagine you have frJends?" =P

Great comic!

P.S. Although I do agree that i is for loops. :P

correction both i and j are for loops :P

you mean jmagjne?

this is the one thing i really really hate intro electrical engg courses for, i mean they would cut marks if you out of habit used i instead of j, i mean fu*k 'em

As a second year engineering student speccing electrical in third-year, the j convention really bugs me. Some day I will invent a problem involving imaginary unit j, unit vector j, and then a few of those random inertia/torque/moment J's from mechanics.

See? Jt iust proves that we need more symbols that can be varjables!

I always wondered what they would do if they ever had to use quaternions or, worse yet, octonions.

I took a robotics course in the electrical engineering department that used quaternions. It was my first exposure to i==j . I wish I still had my notes to check. I imagine they just used j,k,l .

Ever noticed how, in this sort of strip, the character being picked on is always "up against a wall"?

Nice touch!

Not cool, Mike.
Not cool.

Guys, I've a question. Isn't it wrong to say that i (or j) equals the square root of -1, for you easily become that 1 = -1? We learned that you can only let i (or j) be defined so that i² = -1.

Yup that's true, it's much better to use the i² = -1 definition. However, there are a few textbooks that use the radical symbol and in some contexts it is written with a radical. You just have to be careful with that notation though. :P

The biggest problem with this is that i dne sqrt(-1) that is a common error to make -> i^2=-1 is much more correct. Here's an example as to why: -1=i^2=i*i=sqrt(-1)*sqrt(-1)=sqrt((-1)*(-1))=sqrt(1)=1=> -1=1 i=+/-sqrt(-1) I believe is more correct?

I like how mathematicians can spell but can't count.

Band name idea: Jmaginary Engineers
In IPA, [j] sounds like [i],
also in Polish and Esperanto

Forgive me if this is a dumb question, but why do electrical engineers use imaginary numbers?

Dealing with periodic waveforms / movement, as well as sampling data. It is kinda our bread and butter

Must not offend engineers...

Thjs js stupjd.

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Hello my fellow math geeks. My name is Mike and I am the creator of Spiked Math Comics, a math comic dedicated to humor, educate and entertain the geek in you. Beware though, there might be some math involved :D

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