Faraday Cage

A volunteer from the audience climbs into a grid cage through a small door. When the door is closed, every side of the cage, from top to bottom, is cover by a fine grid or by metal plates.
While dramatic music is played, a Tesla transformer placed in front of the cage is turned on. Electric flashes are emitted from both sides of the cage without the person inside feeling anything.

How does it work?
The cage acts as a so-called Faraday Cage, which conducts electricity but only on the outside. It is in fact possible to touch the cage without getting an electric shock! Inside the cage there is no electric field, so nothing happens to the volunteer inside.
The spark plugs in an internal combustion engine ignite petrol by generating sparks, which are also produced by a high voltage.