Question: how does a plasma ball work

Angus Cook answered on 21 Jun 2016:

Plasma balls are usually filled with a noble gas, like neon (we call it a noble gas because it’s generally pretty chemically unreactive). The little ball in the middle of the glass or plastic sphere is an electrode which is generating a high voltage alternating current (2-5 kV at about 30 cycles per second might be typical).

Because of the high voltage the gas around the electrode can be ionised. The gas is made up of atoms, consisting of protons and neutrons in the nucleus, with electrons orbiting around the outside (a little bit like the Sun (nucleus) and the planets (electrons).). Importantly he protons are positively charged, and the electrons are negatively charged. The two charges are opposite, so if you have one proton and one electron then the charge is balanced out, and so the overall charge is zero. A strong enough voltage can cause some of the electrons to become separated from the rest of the atom, and this means that the charge on the atom is not balanced any more. These atoms with a missing electron (or two, or three!) are called ‘ions’, which is why we call this process ‘ionisation’.

Because we’ve got charged particles floating around freely now, they can conduct electricity. A circuit is set up between the electrode in the middle of the ball, and the air (and eventually the ground) around the outside of the ball. Because the gas around the electrode not allows electrons to move freely, they’re accelerated between the electrode and the outside air by the alternating current. This causes the gas to heat up, because it keeps getting hit by the electrons tearing back and forth between the electrode and the outside air, and as it heats up it starts to glow.

When you touch the outside of the plasma ball, you’re essentially placing yourself as part of the circuit. You are a much better conductor than air, and so the current the glowing strands can carry is increased, which means that they can carry more electrons, which means more collisions, which means brighter strands.