Big, Fat Electronics question for all y'all.

[footfootfoot]

Here's my latest question, it's an electronics question. Not my strong suit, I could hold my own back in junior high school, but I think that had rather more to do with me being put in a class with riders of the short-ish, if not completely truncated, bus.
Zippy was onto something when he sussed out my yeast ranching ambitions. I've been trying to build a DIY magnetic plate stirrer for yeast culturing. It seems that every dick and his dog has made one that works and then put up a youtube video of it stirring smugly.

I've got a couple of DC fans from inside a junked 'puter.
1) a 12V 0.4amp
2) a 12V 0.3amp

I also got a 10k Ohm audio taper pot, 250V DC .25 Watt

When I powered it up with my 12V .3amp power supply the pot started smoking. What's up with that?

I thought I had all my shit in one sock, but it seems like I didn't.

It's a three terminal pot and I had it wired correctly: line-in load-out.

Any electronic adepts out there? Any magnetic plate stirrers at Ye Olde Pawne Shoppe?