Hi Clare -
I wired up a mains plug with everything possible wrong with it and asked people to spot as many things as they could.
(8 things wrong with this!)
A multimeter and a bag of fuses to test, including just one or two dead ones is good and can amuse quite young kids. And a bunch of batteries to test, some good, some not so good and some bad, likewise.
A portable CD player or similar gadget with all (or practically all) the screws taken out so you can demonstrate disassembly and point out the main components such as the laser, spindle and leadscrew motors, power supply, electrolytic caps etc.
A component tester such as one of these plus a bag of assorted components can be a good converstation starter.
If you can’t find all 8 faults with the plug, here’s the answer:
簺籃籌类籪籬籴籮籭 籹籵籾籰 籼籱籮籵籵簷
簻籃籗籸 籼籬类籮粀 籲籷 籮籪类籽籱 籹籲籷 簱籪籵籵 籼籬类籮粀籼 籶籾籼籽 籫籮 籽籲籰籱籽簲簷
簼籃籗籸 籯籾籼籮簷
簽籃籕籲籿籮 籪籷籭 籷籮籾籽类籪籵 粀籲类籮籼 籼粀籪籹籹籮籭簷
簾籃籋类籸粀籷 粀籲类籮 籲籷籼籾籵籪籽籲籸籷 籼籽类籲籹籹籮籭 籫籪籬籴 籽籸籸 籯籪类簷
簿籃籋籵籾籮 粀籲类籮 籭籲籽籽籸簵 籪籷籭 籱籪籼 籵籸籸籼籮 粀籱籲籼籴籮类籼簷
籀籃籌籪籫籵籮 籬籵籪籶籹 籼籱籸籾籵籭 籰类籲籹 籽籱籮 籸籾籽籮类 籼籱籮籮籽籱 簱籪籷籭 籫籮 籽籲籰籱籽簲簷
籁籃籋类籸粀籷 粀籲类籮 籱籪籼 籫籮籮籷 籴籷籲籬籴籮籭 籸籷 类籮籶籸籿籲籷籰 籽籱籮 籸籾籽籮类 籼籱籮籪籽籱簷
(Translate from Chinese at https://rot8000.com/Index)