So I couldn't resist. I figured I'd give it a try since I happened to have a one of those million candlepower rechargeable 6v flashlights sitting right beside me. Popped the bulb out, hooked it up and presto! A million candles courtesy of my legs.
Funny: I could see the light pulse on each down stroke of the pedal. I'll have to wear my bike shoes and clip in if I want to apply smooth power all the way around.
So then I hooked up the voltmeter to see how much the physical effort corresponded to the output. And then it immediately became a game of "what voltage corresponds to what amount of light output", which immediately became a game of "I guess 8v is too much voltage for a 6v bulb". Oops.
It was funny though: when the bulb expired, the pedal effort immediately became easier. But powering the light certainly wasn't "hard". I wish I could have taken a current reading to know how many watts I was pushing before it blew up.
Next steps:
Commence the junk car battery hunt tomorrow!