A Van de Graaff generator is a device that has a large spherical device on top of a column. Inside this column is a silk belt that runs on two metal pulley wheels. The electons are stripped from the wheels and a positive charge is induced and stored upon the large sphere at the top. A wand with an electical wire attached to the bottom may be drawn along the large sphere, and when the electical potential overcomes the distance between the two charges, a spark of electicity jumps from the large sphere to the metal wand. These charges are not life threatening, people may place their hands on the large sphere and have the static charge passed through their bodies to experience their hair standing on end due to the electric shock. Such minimal charges are subject to loss by leakage. Leakage may be minimalized by having the system as far from the floor as possible, since the floor would ground the system. Another factor that leaks charge is water vapor in the air (humidity), so these experiments have their best results on less humid days.