Just don't want to screw this up...
Which is correct? A or B?
There may be a convention, but I see no reason why there SHOULD be a convention. You need the data sheet. The manufacturer's (and therefore the ONLY) part number for a digikey 497-2753-5 is actually STPS1545D.
Here's the data sheet. Look at the very first page. (There's even a picture!)
Again, I see no reason why this should be the convention for ALL daiodes in TO-220 cases. But it MIGHT be.
If you're still unsure, measure teh resistance with a multimeter. It will have infinite resistance one way and low resistance teh other way. That'll tell you which direction it conducts.
What is a convention... and I couldn't find it on the data sheet! Except fot the K and A on the pins... What is K and A?
Arrgg!! This is the last thing to solder! Just tell me which way it goes!!! :)
Convention - just because a diode is in a TO-220 case doesn't mean that internally there all wired the same! If they were, that would be "convention."
OKay. K=Cathode (the negative end with the wiggly line on) A=anode (the positive end which is the end where the little arrowhead points AWAY from).
With respect to your pop quiz, B is the answer, but with respect to convention, I'm saying you shouldn't assume this is the case for all diodes.
Gimp not as fast as Google 8-(
If I'd known it was a race, I'd have produced a ray-traced short video of the answer. I can see it now. The part spinning on the screen, the plusitive and minusive ends glowing. Electrons whizzing on their merry way. Getting stopped by the wiggly line...
I could have been big. BIG, I tell you.
In the time it took you guys to poke eachother... I GOT IT SOLDERED!!!!!! DONE!!!!!
Now comes the blue smoke -- I am so excited!
Dude, magic smoke is what it's all about.
I like it better with caps, you even get confetti with it!