Elektor Spiral Micro, Tesla sparks from a USB charger

To generate these spectacular sparks they used devices known as Tesla coils — named after the physicist and engineer Nikola Tesla. Most of the Tesla coils have in common that they’re quite large and potentially dangerous. There is a lot of energy involved, which makes the chances of a serious shock and/or burns very possible. When we want to make a (relatively) safe Tesla coil we must therefore limit the amount of energy used. In contrast to what the free-energy advocates want us to believe, it is never possible to extract more energy from a system than what was first put into it.