High tech comes to Am Sci & Surp!! It is here in the form of a Peltier junction, a thermo-electric device that translates electric power into heat, and perversely, into cool. Apply current at 15VDC to the gizmos and they extract thermal energy from one face, thereby cooling it. The heat is dumped onto the other face, thereby heating it. Please note: you must use a heat sink on the hot side or the junction will fry itself, since it can quickly create a 65° C temperature differential in a no load situation. Stack two, or build a cascade to increase the thermal differential created. Or run it backwards. Apply heat or cold to the relevant face and produce a current. Amazing for science projects and experiments. Practical for coffee warmers, beer coolers and mini-refrigerator or warming oven applications. They come with a datasheet. 1-9/16" sq. x 3/16" thick and draws 6A.

From Therm-O-Disc, this thermal cut-off switch is N/C (normally closed) by definition. (Thermal cut-offs are what keep your coffeepot from burning your house down.) This one shuts down between 221°F (105°C) and 248°F (120°C) and measures 5/8" dia x 9/16" thick, with (2) axial terminals.

This dipped, nominally 10K Ohm thermistor is on a heatshrunk and tubed 27” lead with a 6mm 2-pin Molex connector. Resistance drops as heat increases (NTC). AC takeout.