Conductors and insulators

For teaching electrical conduction I use a singing gonk type thing - forgotten the name of them (anyone remember?), but they have a electrode on each hand and when you touch both hands it sings 'girl you really got me.' Best thing is if you get all of the class in a ring touching each other hands - noses you name it - If the circuit is complete it will sing round a loop of 25 kids. having a break in the chain with two students holding various conductors insulators will make it sing / not sing. They love it!