Safety of a Faraday cage. Amid a flurry of electric discharge, a museum worker demonstrates the safety of a Faraday cage. The cage is designed such that no discharges will reach inside. The distance between the bars means that a discharge will always find it easier to hit a bar than pass in between to another object. The person inside is therefore protected. The discharge is created by a vast Van de Graaff generator (columns and spheres) behind the cage, with a potential difference of 2.5 million volts. The generator was built by Van de Graaff in 1931, and is now at the Boston Museum of Science.