[waltwalther]

This brought back a great memory from my childhood. When I was a boy, in fourth or fifth grade, my dad showed me how to give my friends an electrical shock with a transformer and a 9-volt battery.

I made the design my own by mounting the transformer to a 4x4 piece of scrap plywood, and then cutting out two square 'finger pads' from a tin can, and screwing those into the plywood also.

Add in some wire, a switch, a battery, and a little patter, "place your two fingers on the shiny pads and this will make music....using your mouth as the speaker" and your parents get a call from the principal.

Honestly, I always thought I was the only one who did this. My dad was a practical joker with a sense of humor that only he understood.

My dad died last February. This was a wonderful memory that made me smile. Thanks Hacker News for two memories in a weeks time!

[Grazester]

My cousins did this to me as a kid. I thought it was great that a little battery could give such a huge jolt simply reversing the input side of a step down transformer to the output side. As kids we had rudimentary knowledge of what a transformer did since our country used 220v but most of our electronics came from the U.S. and needed a step down transformer.

[waltwalther]

...and it really is a pretty good jolt if I remember correctly. After reading this post I considered rebuilding my project and showing it to my wife....but that's probably a bad idea lol.