How's this? Grab a glass jar, fill with water and a salt of your choice, say, bicarbonate of soda, drop two electrodes into it (stainless steel or carbon is good; aluminum will tend to polarize after awhile and form a leaky rectifier). Apply current and watch for bubbles and/or steam. Vary resistance by varying the distance between electrodes. Or use a dill pickle instead if you like glowing pyrotechnics. We will always have appliances with heating elements floating around that can be pressed into use, particularly where higher-power loads are concerned. What I don't like about incandescents used as a load-limiter is the very low cold resistance. I'd much rather have a "soft" start--but then carbon-filament incandescents haven't been easy to find for the last 80 years or so. Cheers, Chuck