Plasma balls are often used to demonstrate the physics of electrical currents in school science laboratories. They consist of a thick clear glass sphere that contains a high voltage electrode (Tesla coil) at its centre. The sphere is filled with a mixture of inert gases such as neon, argon, xenon and krypton under a partial vacuum and is powered with a low-voltage power supply. When the plasma ball is operational, beams of coloured light are produced that extend from the high voltage electrode to the outer glass sphere as the gases inside ionise1, 2, 3. An electromagnetic field is also produced around the ball which diminishes with distance from the electrode4.
Plasma balls are generally regarded as safe devices, however, when dealing with any apparatus that generates an electric current there are several safety measures that should be implemented. Plasma balls are sources of small levels of current, static charge and electromagnetic waves that can pose a hazard for some users and certain electrical devices 4, 5, 6.
Safety notes on the use of plasma balls
- Ensure that anyone who has a heart condition, medical device such as a pacemaker, implanted defibrillator, cochlear implant or hearing aid does not touch the plasma ball3. When touched with the hand a small, current will pass from the ball to earth through the body. This current can interfere with the operation of medical electrical devices. One reference recommends that people with specific medical devices should observe from a distance of at least two metres away.7
- Do not leave your hand on the ball for any length of time as a significant amount of heat will be generated.
- Never handle the ball with wet hands as a shock may be produced6.
- Keep electronic devices such as mobile phones and computers away from an operating plasma ball as the frequencies that are produced may interfere with their function8.
- Keep away from metal surfaces, metal objects and remove any metal jewellery before operating a plasma ball. Touching anything metal whilst touching the ball will generate a small static shock6. Any metal object that touches the ball will rapidly heat up and can cause burns and fires8.
Some suitable activities (observing the above safety notes):
- Observe the different patterns created by placing:
- One finger; or all your fingertips or your whole palm on the plasma ball
- Your hands in different positions on the plasma ball
- Observe a fluorescent tube illuminating:
- Hold one end of the glass part of a fluorescent tube (NOT the metal cap) and bring the tube close to and gently rest the other end (NOT the metal cap) on the plasma ball.
References and further reading:
1’An Introduction: What is a Plasma Ball and How Does it Work?’, ScienceStruck website, https://sciencestruck.com/what-is-plasma-ball-how-does-it-work (Accessed August 2018)
2’’Plasma Ball Experiments’, The Wonders of Physics Traveling Outreach Program, University of Wisconsin –Madison website, https://wonders.physics.wisc.edu/plasma-ball-experiments/ (2008)
3CLEAPSS. 2015. GL194 Using a plasma ball. CLEAPSS website. http://science.cleapss.org.uk/ (Login required.)
4 ‘Plasma: The fourth state’, Science in School website, https://www.scienceinschool.org/content/plasma-fourth-state (2016)
5‘Physics Van – Plasma Ball’, Physics Van, University of Illinois website, https://van.physics.illinois.edu/demos/Plasma%20Ball/Plasma%20Ball.php (Accessed August 2018)
6 Specialty Toys Direct. n.d. Plasma Globe Owner’s Guide, Specialty Toys Direct website, https://www.stdi.ca/amazon/plasma-globes/Plasma%20Globe%20Owners%20Guide%20-%20Web.pdf (Accessed August 2018)
7Reiland, Robert. 2007. Plasma Globes and “Body Capacitance”, Contemporary Physics Education Project website, http://www.cpepphysics.org/fusion-materials/PlasmaGlobe-BodyCap.pdf
8‘Plasma Ball Tricks’, Sciencing website, https://sciencing.com/plasma-ball-tricks-7613499.html (2017)
‘How do plasma lamps work?’, Softpedia news website, https://news.softpedia.com/news/How-do-Plasma-Lamps-Work-77633.shtml (2008)
‘Plasma ball’, Department of Physics, University of Oxford website, https://www2.physics.ox.ac.uk/accelerate/resources/demonstrations/plasma-ball (Accessed August 2018)
‘Plasma Ball – large’, Questacon website, https://shop.questacon.edu.au/Plasma-Ball-Large.html (Accessed August 2018)
‘Plasma globe’, Wikipedia website, https://en.wikipedia.org/wiki/Plasma_globe (2018)
‘Plasma Globes’, ACS Publications – Chemical & Engineering News website, https://pubs.acs.org/cen/whatstuff/86/8643sci3.html (October 2008)
Reiland, Robert. 2002. Studying the Electric Field Near a Plasma Globe, Contemporary Physics Education Project website, http://www.cpepphysics.org/fusion-materials/ElectricFieldNearPlasmaGlobe.pdf