The machine works by pumping electrons from the base to the top . The electrons onto the top sphere, resulting in a very large potential between the top sphere and the discharge sphere. Eventually the gets so big that a jumps from the top sphere to the discharge sphere. The voltage is very high, but the current is . Therefore it is quite safe to use.

If you hold the discharge sphere, you can feel it being towards the machine, just before the spark jumps.

Another trick is to get someone to put their hands on the top sphere and stand in a plastic tray. Their stands on end as the electrons distribute around the hairs, and make them repel.

Air is a good . However at very high potential differences ionisation occurs and the air can . This is called the breakdown voltage. For dry air, the breakdown voltage is 3000 V/mm or 3 × 10^6 V/m (volts per metre). This means that a spark 1 cm long is , while one of 10 cm is 300 000 V.