## A Conversation for Complex Numbers - an Introduction

### Electrical Engineers call it j not i

highamexpat Started conversation Aug 15, 2007

Takes me back to when I was studying electrical engineering quite a few years ago. the letter i is reserved for current so we electrical engineers call it j not i.

it's very useful for carrying out calculations on inductive and capacitive circuits where the resistance is the real part and the inductance is -j & capacitance is +j (inductive current lags the resistive current by almost 90 degrees & vice versa for capacitive.

We also generally convert it to polar coordinates which simplifies multiplication and division if my memory serves me well.

### Electrical Engineers call it j not i

Icy North Posted Aug 19, 2007

Hi highamexpat,

I too studied electrical engineering many years ago - so long in fact, that I forgot to mention this. Many thanks for posting it here!

Those co-ordinate systems always confuse the hell out of me. Did you use those Smith charts, which we plotted things on? If I had some now, I'd give them to my daughter to colour in.

Icy

### Electrical Engineers call it j not i

highamexpat Posted Aug 20, 2007

Hi icy

I never had much problem with with Argand diagrams or complex numbers though Calculus was another story.

I found a great calculator which let you input in the form a+jb & it would do any calculation you wanted & switch between cartesian or polar coordinates at the push of a button.

Never had anything to do with Smith diagrams (that I can remember) the worst ones were those logic charts for Boolean algebra. i could never get my head round them.

Cheers highamexpat

### Electrical Engineers call it j not i

Muddy90 Posted Nov 17, 2008

Blimey

This conversation brings back memories, I spent an age racking my brain over this then I to discovered that calculator.

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### Electrical Engineers call it j not i

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