What to do with a bunch of slightly depleted 9V batteries?

[everettr]

(08-08-2014 03:32 PM)Katie Wasserman Wrote:  Neon bulbs are fun to play with using medium-high voltage DC; you can make some nifty oscillators by adding resistors, capacitors and diodes.

If you don't include a series resistor in the circuit, neon bulbs make great short circuits! I learned about current-limiting as a child when I poked the leads of a bare neon bulb into an electrical socket. There was sound and heat, and as the spots slowly faded from my vision, I remember being slightly puzzled by seeing how short the leads had become.